Optical filter comprising a variable transmittance layer

ABSTRACT

A optical filter comprising a variable transmittance layer having a first spectrum in a dark state, and a second spectrum in a faded state; and a color balancing layer having a third spectrum; each of the first, second and third spectra comprising a visible portion; the first and third spectra combining to provide a dark state spectrum approximating a dark state target color; and the second and third spectra combining to provide a fades state spectrum approximating a faded state target color. The optical filter may further comprise a light attenuating layer. The optical filter may further comprise part of a laminated glass.

RELATED CASES

This application claims the benefit of U.S. Provisional Applications No.61/652,466 filed May 29, 2012, and 61/766,613 filed Feb. 19, 2013; bothof which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates generally to optical filters. The opticalfilter may comprise a variable transmittance layer and a color balancinglayer.

BACKGROUND

Variable transmittance optical filters may employ a variety oftechnologies to alter visible light transmittance. Generally, suchfilters may be switched between a state of higher light transmittance(faded or light state) to a state of lower light transmittance (darkstate) with the application, removal or reduction of a stimulus such asUV light, temperature and/or a voltage. Examples include photochromics,electrochromics, thermochromics, liquid crystals or suspended particles.Some photochromic materials may darken in response to light, frequentlyultraviolet light, and may return to a faded state when the UV light isremoved or reduced. Some electrochromic materials may darken in responseto application of a voltage, and may return to a faded state once thevoltage is removed; alternately, some electrochromic materials maydarken in response to application of a voltage of a first polarity, andfade when a voltage of an opposite polarity is applied. Somethermochromic materials may darken proportionately in response to atemperature increase—for example, the warmer the material, the darker itcan become. The thermochromic material may return to a faded state whenthe temperature decreases. Liquid crystal materials and suspendedparticle devices comprise crystals or particles that alter orientationin response to application of a voltage. In the absence of a voltage,the crystals or particles are randomly oriented, and scatter incidentlight, thus appearing opaque, or transmit very little light. When avoltage is applied, the crystals or particles are aligned with theelectric field, and light may be transmitted. Where the variabletransmittance optical filter includes an electrochromic aspect, thevariable transmittance optical filter may comprise electrical connectorsfor connecting the optical filter to a control circuit, the controlcircuit to provide power to the optical filter to effect anelectrochromic color change.

Depending on the nature of the variable optical filter and its use,further attenuation of the transmitted light or solar energy may bedesirable. Where the variable transmittance optical filter is used onthe window of a vehicle, aircraft or building, reducing or blockingtransmission of infrared light may be useful to control the heat gain,and reducing or blocking transmission of ultraviolet light may be usefulto protect occupants in the vehicle or building. Where impact protectionis desirable, inclusion of laminated glass (“safety glass”) in thewindow may useful.

U.S. Pat. No. 4,244,997 and US 2009/0303581 describe a laminated glasswith a shade band and U.S. Pat. No. 7,655,314 describes a laminatedglass with an interlayer comprising an IR blocking component, and acoloring agent to complement the yellow-green appearance of the IRblocking component, but does not address how the color may bemanipulated in a window with variable light transmission in the visiblerange. Tinted glass in grey, bronze or green tones may also be used toattenuate the light transmitted through a window. Some tints mayattenuate light approximately equally across the visible spectrum, andwhile this may be effective in reducing the overall glare, it may notprovide for color “correction” to a neutral tone if a component of thelaminated glass itself has a color, and additional color correction maybe needed.

Some examples of windows of vehicles that may alter light transmissionor opacity with electricity are known—the Magic Sky™ automotive sunroofis one example of automotive glass that switches from an opaque state toa transparent state with the application of electricity. The switchablelayer (suspended particle thin film) is applied to the sunroof glass andconnected to the vehicle's electrical system. U.S. Pat. No. 6,995,891describes an electrochromic safety glazing comprising an electrolyteinterlayer with a polymeric binder for lamination of the substrates.

Where the laminated glass has a variable transmittance component, thedegree of light transmission in one or both of the faded and dark statesmay be too great, or of a distorted color. Previously, colour balancingof glazing products such as automotive sunroofs and architecturalwindows was accomplished by altering the chemical composition of theglass itself to provide the desired colour, or by including a colouredinterlayer (e.g. PVB) in between two sheets of glass. Altering thecolour of the variable transmittance filter is much more difficultbecause the materials used for producing the variable transmittancecannot easily be changed to different colors while maintaining all ofthe variable transmittance properties. For example, some variabletransmittance filters are blue in colour, which may be suitable for someapplications but not others. Currently, the color of the overall productis determined by the color of the variable transmittance filter, even ifthat color is not seen as the most desirable by customers and potentialcustomers of the product. Inclusion of one or more additional visiblelight filters may further attenuate the transmitted light, but may alsodistort the color or exacerbate an already distorted color.

SUMMARY

The present disclosure relates to an multi-layer composition comprisinga variable transmittance layer and a color balancing layer selected tocombine with the color of the variable transmittance layer in order toachieve a desired colour for the overall stack. A laminated glass withvariable light transmittance, and color balancing layer to provide atarget (e.g., neutral) color in a faded state, a dark state or both afaded and dark state may be a useful addition over the art, and be usedin automotive windows (windshields, sunroofs, moonroofs, windows,backlites, sidelites or the like), architectural applications,ophthalmic devices or applications, or the like.

In accordance with one aspect, there is provided an multi-layercomposition comprising a variable transmittance layer having a firstcolor in a dark state, and a second color in a faded state; and a colorbalancing layer having a color complementary to a colored state of thevariable transmittance layer. The color balancing layer may have a colorcomplementary to the first color, the second color, or the first and thesecond color of the variable transmittance layer. The color balancinglayer, together with the variable transmittance layer in a dark state ora faded state, or a dark state and a faded state, have a third desiredcolour (e.g., a neutral color). The variable transmittance layer andcolor balancing layer may be laminated inside a polymer layer. Thevariable transmittance layer comprises a switchable film, anelectrochromic material, a photochromic material, a suspended particlelayer or a liquid crystal layer.

In accordance another aspect, there is provided a multi-layercomposition comprising a variable transmittance layer comprising avariable transmittance optical filter having a first spectrum in a darkstate, and a second spectrum in a faded state; and a color balancinglayer having a spectrum; each spectrum comprising a UV portion, avisible portion and an IR portion; and the spectra of the layerscombining to provide a color of the multi-layer compositionapproximating a target color. One or more color balancing layers may beinboard of the variable transmittance layer.

In accordance with another aspect, there is provided a method ofpreparing a multi-layer composition approximating a target color,comprising: providing a variable transmittance layer comprising avariable transmittance optical filter having a first spectrum in a darkstate, and a second spectrum in a faded state; selecting a colorbalancing layer having a spectrum; and combining the variabletransmittance layer and color balancing layer in a stack approximatingthe target color.

In accordance with another aspect, there is provided an optical filtercomprising a variable transmittance layer having a first color in a darkstate, and a second color in a faded state; and a color balancing layer,the first color and color balancing layer combining to provide a darkstate color approximating a dark state target color; and the secondcolor and color balancing layer combining to provide a faded state colorapproximating a faded state target colour.

In accordance with another aspect, there is provided an optical filtercomprising a variable transmittance layer having a first spectrum in adark state, and a second spectrum in a faded state; and a colorbalancing layer having a third spectrum; each of the first, second andthird spectra comprising a visible portion; the first and third spectracombining to provide a dark state spectrum approximating a dark statetarget color, and the second and third spectra combining to provide afaded state spectrum approximating a faded state target colour.

In accordance with another aspect, there is provided a method ofpreparing an optical filter approximating a target color, comprising:providing a variable transmittance layer having a first spectrum in adark state, and a second spectrum in a faded state; selecting a colorbalancing layer having a third spectrum; and combining the variabletransmittance layer and color balancing layer in a stack approximatingthe target color in the faded state, the dark state or both the fadedstate and the dark state.

In some aspects, the color balancing layer is inboard of the variabletransmittance layer.

In some aspects, the optical filter may further comprise a lightattenuating layer. The light attenuating layer may be outboard of thevariable transmittance layer.

In some aspects, the variable transmittance layer comprises a switchingmaterial transitionable from a faded state to a dark state when exposedto electromagnetic radiation, and from a dark state to a faded statewith application of a voltage. The electromagnetic radiation maycomprise a component with a wavelength of 450 nm or less. Theelectromagnetic radiation may comprise a component with a wavelength ofbetween 400 and 450 nm. The voltage applied may be from about 1.1 toabout 2.5 V, or any amount or range therebetween.

In some aspects, the variable transmittance layer comprises a switchablefilm. The switchable film may comprise a switching material. Theswitching material may be part of a switchable film, the film comprisinga first and a second transparent substrate, a first and second electrodedisposed on a surface of the first, second or first and second substrateand a switching material disposed between the first and secondsubstrates and in contact with the first and second electrodes. Theswitching material may comprise a thermoset polymer, an ionic medium andone or more photochromic/electrochromic compounds, the switchingmaterial transitionable from a faded state to a dark state when exposedto electromagnetic radiation, and from a dark state to a faded statewith application of a voltage.

In some aspects, the color of the optical filter is a neutral color inthe dark state, the faded state, or both the dark state and the fadedstate. In some aspects, the variable transmittance layer and colorbalancing layer are encapsulated in a polymer. The optical filter mayfurther comprise an infrared (IR)-blocking component, an ultraviolet(UV) blocking component, or a UV blocking component and an IR blockingcomponent.

In some aspects, the optical filter may comprise an LT_(A) in a darkstate of less than about 15%, or less than about 10%, or less than about5%, or less than about 2%, or less than about 1%; and/or an LT_(A) in afaded state of greater than about 5%, or greater than about 10%, orgreater than about 15%, or greater than about 20%; and/or a contrastratio of at least 5, at least 10 or at least 20. In some aspects, theoptical filter may comprise a light transmission value of 1% or less inthe dark state and 6% or higher in the light state, or of 5% or less inthe dark state and 15% or higher in the light state.

In some aspects, the target color of the dark state and color of theoptical filter in the dark state provide a delta C value of from about 0to about 20; and/or a delta E value of from about 0 to about 20. In someaspects, the target color of the faded state and color of the opticalfilter in the faded state provide a delta C value of from about 0 toabout 20; and/or a delta E value of from about 0 to about 20.

In some aspects there is provided a laminated glass, an automotiveglazing, an opthalmic device or an architectural glazing comprising anoptical filter.

The color of the optical filter may be a neutral color in a dark state,a faded state, or both a dark state and a faded state. The colorbalancing layer may have a color complementary to the first color, thesecond color, or the first and the second color of the variabletransmittance layer. The variable transmittance layer and colorbalancing layer may be laminated inside a polymer layer.

The optical filter or laminated glass may further comprise anIR-blocking component and/or a UV blocking component; the IR blockingcomponent and/or a UV blocking component may be outboard of the variabletransmittance layer. Where a light attenuating layer is present, the IRblocking component and/or the UV blocking component may be inboard, oroutboard, of the light attenuating layer. In some aspects, the UVblocking layer may be a light attenuating layer.

To provide an optical filter with one or more of a selected contrastratio, dark state color, or light transmittance, a variabletransmittance layer and a color balance layer may be combined with oneor more of a light attenuation layer, UV blocking layer (e.g. a cutofffilter of a selected wavelength), an infrared blocking layer or thelike. A color balance layer may be selected to absorb light in theregion of the spectrum where the variable transmittance layer has alesser absorbance. Depending on the intended application, it may bepreferable to achieve a darker dark state; for such an embodiment, andoptical filter may include a grey glass or grey film light attenuatinglayer. This may reduce light transmittance in a faded state, thereforeif maximum contrast ratio is desired (a lighter faded state and a darkerdark state), a color balancing layer that selectively complements thespectrum of the variable transmittance layer may be preferable to a greyglass or grey film. Where increasing weathering durability is preferred,inclusion of a cutoff filter of 420 nm or greater in an optical filtermay be useful. In some aspects this may provide a further advantage of agreater light transmittance in the dark state.

This summary does not necessarily describe the entire scope of allaspects. Other aspects, features and advantages will become apparent tothose of ordinary skill in the art upon review of the followingdescription of specific embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features will become more apparent from the followingdescription in which reference is made to the appended drawings. Thefigures are for illustrative purposes, and unless indicated otherwise,may not show relative proportion or scale.

FIG. 1 shows light transmission profiles of S109 in dark (solid line)and faded (dashed line) states, according to one embodiment.

FIG. 2 shows light transmission of an interlayer comprising S109 with acolor balancing layer. Dark state—solid line; faded state—dotted line;color balancing layer—alternating dot/dash line, according to anotherembodiment.

FIG. 3 shows a sectional view of an apparatus according to anotherembodiment.

FIG. 4 shows a sectional view of an apparatus according to anotherembodiment.

FIG. 5 shows a sectional view of an apparatus according to anotherembodiment.

FIG. 6 shows a sectional view of an apparatus according to anotherembodiment.

FIG. 7 shows sectional views of various apparatus configurationsaccording to other embodiments.

FIG. 8 shows a schematic view of an apparatus according to anotherembodiment.

FIG. 9 shows the transmission spectra from 10 commercial sources of‘grey’ glass, demonstrating a maximum C value (Cmax) of 4.4, with anaverage C value (Cavg) of 1.6, according to an embodiment.

FIG. 10 shows a schematic diagram of the cut edges, busbar andelectrical leads for a variable transmittance layer as a top view (a)and as a sectional view, along line A-A (b), according to anotherembodiment.

FIG. 11 shows light transmission spectra for each of four lightattenuation layers—Rosco 07 Pale yellow—solid line; Gamcolor 1543 FullCTO—dotted line; Rosco 4390 CalColor 90 Cyan—dotted line; Rosco 398Neutral Grey-long dash-dot line, according to another embodiment.

FIG. 12 shows the alteration of the spectra of a modeled ‘stack’ in darkand faded states with a color balance layer selected to provide a targetLT_(A) in the dark state and color in the faded state. Dark state—solidline; faded state—dotted line; color balancing layer—alternatingdot/dash line, according to another embodiment.

FIG. 13 shows the configuration of various optical filters, according toanother embodiment.

FIG. 14 shows a plot of internal temperature of the optical filters ofFIG. 13 according to another embodiment. Stack A—solid diamond; stackB—solid square; stack C—solid triangle: stack D—open square: stackE—open triangle; Stack F—solid circle: Stack G—open circle.

FIG. 15 shows a plot of weathering performance of test devices exposedto a QSUN Xenon arc light source with a black panel temperature setpoint of 50° C. and 70° C. X-axis-total energy exposure at 340 nm(MJ/m²); Y axis % initial darkening performance. Solidcircles—weathering at 50° C. (slope Y=−1.938×+99.131); soliddiamonds—weathering at 70° C. (slope Y=−18.612+152.2), according toanother embodiment.

FIG. 16A shows a bar graph of darkening performance of alpha 6.1f PVBlaminated test devices exposed to a QSUN Xenon arc light source with ablack panel temperature set point of 70° C. with a UV blocking layer ofspecified cutoff wavelength, normalized to the darkening performance forthe test specimen with a UV blocking layer with a 390 nm cutoff (50%+/−6nm). FIG. 16B shows a bar graph of the delta E of the faded state forthe same set of test devices. The delta E values were normalized to thefailure point (80% of initial darkening performance) of the testspecimen with a 390 nm cutoff filter (50%+/−6 nm), according to anotherembodiment.

FIG. 17 shows a plot of chromophore S158 absorbance (solid line) (leftside Y axis; transmittance right side Y axis) for various wavelengths oflight. A series of cutoff filters (50%+/−6 nm) at 370 nm (dashed line),400 nm (dotted line), 420 nm (long dashed line), 435 nm (long dash, 2dots line) and 455 nm (long dash-dot line), according to anotherembodiment.

FIG. 18 shows a bar graph of the minimum light transmittance in darkstate in the absence or presence of cutoff filters, according to anotherembodiment.

FIG. 19 shows a bar graph of the time to reach minimum lighttransmittance in the absence or presence of cutoff filters, according toanother embodiment.

DETAILED DESCRIPTION

There is provided, in part, a optical filter comprising a variabletransmittance layer having a first spectrum in a dark state, and asecond spectrum in a faded state' and a color balancing layer having aspectrum; each spectrum comprising an ultraviolet (UV) portion, avisible portion and an infra-red (IR) portion; and the spectra of thelayers combining to provide a color of the optical filter approximatinga target color. There is further provided, in part, a laminated glasscomprising such a optical filter.

Optical filters according to various embodiments may have low powerrequirements for switching between dark and faded states. The opticalfilter may be useful for a variety of applications such as opthalmicdevices (e.g. visors, masks, goggles, lenses, eyeglasses (prescriptionor not) or the like), architectural windows, vehicle windows andglazings (including windshields, side lite, side or rear windows), andvehicle sunroofs of various types including pop-up, spoiler, inbuilt,folding sunroofs, panoramic roof systems or removable roof panels. Theoptical filter may demonstrate relatively rapid switching between darkand light states, which may be advantageous in applications wherefrequent or rapid changes in lighting conditions occur. The opticalfilters may be stable and exhibit minimal change in light transmittancein response to temperature, which may be advantageous in applicationswhere frequent or rapid changes in temperature conditions occur. Theoptical filters may exhibit photostability and durability suitable foruse in various applications, including those referenced herein, and maybe cycled between light and dark states many times. In some embodiments,the optical filter may be incorporated into a mirror or display. Thelight transmittance of the optical filter may be varied to control theamount of light reaching the mirror, reflected by the mirror, or both,or to control the amount of light emitted by the display. There isfurther provided, in part, for an automotive glazing or architecturalglazing, comprising the optical filter. The optical filter may furthercomprise a light attenuating layer.

A user may control the light transmissibility of an optical filter bycontrolling the voltage applied to the composite optical filter, thelight it is exposed to, or both. Voltage may be applied continuously, orintermittently to switch the optical filter from a dark to a fadedstate, or to maintain the optical filter in a faded state.

A spectrum refers to a characteristic light transmission of an opticalfilter or component of a optical filter. The transmitted light may havea UV, a visible and/or an IR component or portion. As examples, FIG. 1illustrates a visible portion of the spectra in the dark and faded stateof a variable transmittance layer comprising S109 switching material.FIG. 2 illustrates a visible portion of the spectra of an optical filtercomprising the variable transmittance layer of FIG. 1 and a colorbalancing layer. The spectrum of the color balancing layer is alsoshown. Spectra from layers may be combined by addition, multiplicationor subtraction of the transmitted wavelength values, and the visibleregion of the resulting spectrum may be described with reference tocolor (e.g. with L*a*b* values, LT_(A), delta (A) C, delta E or thelike).

A variable transmittance layer may comprise a variable transmittanceoptical filter. A variable transmittance optical filter may be based onphotochromic/electrochromic materials which darken when exposed toelectromagnetic radiation (“light”) and fade when a voltage is appliedto the material. Some photochromic/electrochromic materials may alsofade when light of a selected wavelength is incident on the switchingmaterial. The light transmitted by a variable transmittance opticalfilter in a dark or a light state may be altered by one or more colorbalancing and/or light attenuating layers. In some embodiments, theoptical filter may be a film (a multi-layer film). In some embodiments,the optical filter may comprise a rigid component, such as a layer ofglass. The optical filter may be laminated to, or between, betweenlayers of glass using one or more adhesive layers. In some embodiments,the layers of a optical filter (e.g. variable transmittance layer, colorbalancing layer, light attenuation layers, adhesive layers or the like)between two layers of glass may collectively be referred to as an“interlayer”.

The term ‘stack’ may be used generally to describe an arrangement of twoor more layers (glass, interlayer, color balancing layer, lightattenuation layer, adhesive layers or the like), one on top of theother, through which light is transmitted. The stack may be describedwith reference to color, spectrum, transmitted light or a differencebetween the color or transmitted light of a stack, relative to a target(LT_(A), L*a*b*, delta C, delta E or the like).

Generally, a window comprising a variable transmittance component (e.g.a variable transmittance optical filter, variable transmittancelaminated glass or the like) may separate an interior space from anexterior space. It may be desirable to alter the observed color of thewindow, or the color of the transmitted light, to match or approximate atarget color that is different from the color of the variabletransmittance layer. For example, it may be desirable to match orapproximate a target color to harmonize the appearance of the windowwith a building envelope or the exterior color of a vehicle, or toharmonize the appearance of the window with other components of thewindow such as the frame. FIGS. 3-8 illustrate examples of variousconfigurations and arrangement of the layers in an optical filter thatmay be used for such windows. In some embodiments, the relative positionof the layers may be described with reference to the variabletransmittance layer, the incident light, or a space defined in part bythe window. For example, in reference to FIG. 3, a color balancing layer14 is inboard of a variable transmittance layer 16—layer 14 would becloser to the interior space if this were part of a window installed ina building or vehicle. Similarly, a layer 12 is outboard of the variabletransmittance layer 16. Incident light from a light source may benatural or simulated sunlight, or may be artificial light from anysource. The incident light may comprise some or all of the full visiblespectra, and largely exclude light outside the visible spectra, or theincident light may comprise a UV and/or infrared/near infraredcomponent.

Color and Light Transmission of Layers:

The color of a switching material, layer, an optical filter or alaminated glass comprising an optical filter may be described withreference to colour values L*a* and b* (in accordance with IlluminantD65, with a 10 degree observer), and/or with reference to the visiblelight transmission LT_(A) (luminous transmission, Illuminant A, 2 degreeobserver). LT_(A) and L*a*b* values may be measured in accordance withSAEJ1796 standard. The L*a*b color space provides a means fordescription of observed color. L* defines the luminosity where 0 isblack and 100 is white, a* defines the level of green or red (where +a*values are red and −a* values are green), and b* defines the level ofblue or yellow (where +b* values are yellow and −b* values are blue). Anincrease in b* value indicates an increase in the yellowness of thematerial, while a decrease in b* indicates a decrease in the yellownessof the material. An increase in a* value indicates an increase in theredness of the material, while a decrease in a* value indicates adecrease in the redness of the material. For reference to neutral greys,the transmitted color may be describe relative to L*, by calculating C(or C*ab) value, where C=(a²+b²)^(1/2). For example, a transmitted lightdescribed as having an L* of about 40 to about 60, an a* of about −10 toabout +10 and a b* of about −10 to about +10 (describing an area aboutthe centre of CIELAB coordinate system) may be perceived as ‘neutral’,or not substantially red/green or blue/yellow.).

A spectrophotometer may provide information concerning a materials lighttransmittance or absorbance at a selected wavelength or over a range ofwavelengths. Absorbance and transmission of light are related throughthe Beer-Lambert law. Transmission spectra may be converted to anabsorption profile (spectra) according using equation (1):

$\begin{matrix}{A = {{- \log}\; 10\left( \frac{I}{I_{o}} \right)}} & (1)\end{matrix}$

Absorbance values may be converted to transmission in a similar manner.

Generally, intensity of color increases with the amount of chromophorein a switching material, and LT_(A) in a dark state decreases. Where adarker optical filter is desired, this trend may be beneficial, howeverreduction of the amount of chromophore may be also desirable from a costperspective.

To describe a scalar relationship between a target color and the colorof an optical filter, ΔC (delta C) may be calculated:deltaC=C* _(ab) of optical filter−C* _(ab) of target.

To describe a vector relationship between a target color and the colorof an optical filter, ΔE (deltaE) is calculated:deltaE* _(ab)=[(delta L*)²+(delta a*)²+(delta b*)²]^(1/2)

As an example to illustrate the range of C values that may be useful forautomotive sunroofs according to some embodiments, transmission spectrafrom 10 commercial sources of ‘grey’ glass were obtained (normalized forLT_(A)), demonstrating a maximum C value (Cmax) of 4.4, with an averageC value (Cavg) of 1.6, but with substantially similar reduction ofLT_(A) across the entire visible spectrum (FIG. 9). Other L*a*b* valuesover a range of grey tones are addressed below. Thus, a neutral colormay be described as ‘achromatic’(having a similar, or approximatelysimilar LT_(A) over the visible range). When judged “by eye”, a neutralcolor is not substantially yellow/blue or red/green. The lower thedeltaC or dcltaE value, the lesser the difference in color between thetarget color and the color of the stack. Generally, a stackapproximating a target color will have a delta C of about zero to about20, or any amount therebetween, or a deltaE of about zero, or any amounttherebetween. A range of about zero to about 20 or any amounttherebetween includes, about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18 or 19, or any amount therebetween.

Generally, there are no limitations to the color of an optical filter ina faded or dark state—generally the faded state will be substantiallycolorless, or faintly colored and substantially colored in a dark state.Generally, intensity of color may increase with the amount of compoundin the switching material. Where a neutral color of the optical filteris desired, one or more additional layers may be included to alter thetransmitted light. Some layers may reduce the overall lighttransmission—as illustrated in FIG. 9, grey glass reduces thetransmitted light a similar amount across the 380-780 nm range—whereassome layers selectively transmit light for only a portion of the visiblerange. A layer may comprise a static (non-switching) color filter.Further, even though two filters may appear alike to the eye or undersome lighting conditions, they may demonstrate spectra that differsignificantly in some wavelengths thus it may not be readily apparentwhich filters may be suitable. Further, some filters may block ortransmit portions of light (UV, VIS and/or IR) to combine with lighttransmitted by a variable transmittance optical filter. What spectra ofa color balancing layer may be suitable may be dependent on the spectraof the variable transmittance layer.

According to some embodiments, an optical filter, may have an LT_(A) ofless than about 1%, or less than about 2% or less than about 5% or lessthan about 10% in a dark state. According to some embodiments an opticalfilter may have an LT_(A) of greater than about 5% or greater than about10% or greater than about 15% or greater than about 20% in the fadedstate.

According to some embodiments, an optical filter may have an LT_(A) offrom about 1% to about 10%, or any amount or range therebetween in thedark state, and an LT_(A) of from about 5% to about 30% in the fadedstate, or any amounts or ranges therebetween. For example, the opticalfilter may have an LT_(A) in a dark or faded state of about 1, 2, 3, 4,5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 25 or 30%, or any amount or rangetherebetween, with the proviso that the dark state has a lesser LT_(A)than the faded state.

Where the target is a neutral colored ‘stack’, an optical filteraccording to various embodiments may have, in a faded state, an L* valueof about 40 to about 60 or any amount therebetween; an a* value of about−10 to about 5 or any amount therebetween; and a b* value of about −1 toabout 5 or any amount therebetween.

A layer outboard or inboard of the variable transmittance layer willalter the amount and color of the transmitted light; a layer placedinboard of a variable transmittance layer may be referred to as a colorbalancing layer, whereas a layer placed outboard of the variabletransmittance layer (a light attenuating layer) will alter thecomposition of the light incident on the variable transmittance layer,in addition to affecting the amount and color of transmitted light. Acolor balancing layer comprises a spectrum that combines with thespectrum of the other layers in the stack to provide a color thatapproximates a target color. In some embodiments, the color balancinglayer may be of a color complementary to that of the variabletransmittance layer in a dark state, faded state, or both a dark and afaded state. In some embodiments, the color balancing layer complementmay the other layers of the stack, to create approximately equaltransmission in the stack spectrum, particularly in the ˜410-500 nm and˜530-645 nm ranges.

The light attenuating layer may influence, for example, photostability,photostationary state (PSS) or switching kinetics, and/or the overallLT_(A) of the stack. A balance is sought between sufficient high energylight to effect the photochromic darkening reaction, reducing theincidence of higher energy wavelengths to improve lifetime of materials,and achieving a suitable LT_(A) of the stack. In some embodiments, thelight attenuating layer comprises a spectrum that combines with thespectra of the other layers in the stack to provide a color thatapproximates a target color. In some embodiments, the light attenuationlayer may be a neutral grey (e.g. grey glass), or may be a grey staticfilter, or may be a colored static filter selected to attenuate aportion of the incident light for manipulation of the composition of thelight reaching the variable transmittance layer. This selectiveattenuation of incident light may alter the fading ability or fadingspeed of the switching material of the variable transmittance layer. Insome embodiments the light attenuation layer may selectively block aportion of incident light in the UV, or higher energy visible range.

The color of the color balancing layer and/or the light attenuationlayer may provide a color complementary to that of the variabletransmittance optical filter in a dark state, a faded state or a darkstate and a faded state. The light attenuation layer may be outboard ofthe variable transmittance optical filter, and the color balancing layeris inboard of the variable transmittance optical filter—the color of thetransmitted light is manipulated by the interaction of all three layers,whereas the light reaching the variable transmittance is manipulated bythe light attenuation layer. Additional layers may be included in theoptical filter.

Two or more spectra may be described as ‘complementary’ when theyprovide an achromatic, or apparently achromatic spectra (“neutralcolor”) when the visible portions of the spectra are combined.

Photostability of switching material, or components thereof, may beimproved if higher energy wavelengths of light are attenuated. Some UVblocking materials may reduce or eliminate light below about 380 nm,however a balance may need to be achieved between restriction of thelight of about 420 nm or less (to improve photostability of theswitching material) and transmission of sufficient light in this rangeto effect a photochromic switch to a dark state, for a material having aphotochromic aspect. Maximum transmission of light above this range mayallow maximizing of LT_(A) of the stack. Photostability of the switchingmaterial may also be improved by reducing overall the amount of visiblelight reaching the switching material—a filter that reduces some of theincident light up to about 650 nm, may improve photostability, whilepreserving sufficient higher energy wavelengths to effect thephotochromic switch, and maximizing the LT_(A). For example, attenuationof light in a portion centered about 650 nm may reduce the amount oflight absorbed by the chromophore, that would effect a photochromictransition to a faded state (photofading). By attenuating light in thisregion of the spectrum, the photostationary state of the chromophore maybe improved (a darker dark state). Conversely, attenuation of light inthis region may also aberrantly affect fading of switching material byreducing any photofading effect, and making the fading reaction morereliant on electrofading alone. Attenuation of the entire spectrum ofvisible light (by including in a light attenuating layer a grey filteror grey glass, for example) may be advantageous by offering protectionfrom the higher energy wavelengths of light, reduce a photofadingresponse, and/or reducing overall LT_(A) of the stack. In someembodiments, a light attenuating layer may block from about 10% to about90% of light incident on the optical filter.

The fading kinetics of the optical filter may also be altered byinclusion of a light attenuating layer—by reducing or blocking thewavelengths of light incident on the switching material thatphotochromically fades the switching material, a darker (greaterabsorption) photostationary state may be achieved. The fade time of theswitching material may also be increased. By reducing or blocking thewavelengths of light incident on the switching material thatphotochromically darken the switching material, a lighter (reducedabsorption) faded state may be achieved; the darkening time of theswitching material may also be increased.

In some applications, it may be advantageous to have a longer darkeningtime. When electrofading an optical filter in the presence of sunlightthere is a competition between the rate of darkening induced by sunlightand the rate of elcctrofading. In order to achieve the fully faded statein the presence of sunlight, the rate of darkening must be substantiallyslower than the rate of electrofading. A cutoff filter may be selectedwith a cutoff wavelength that combines photostability, extent ofdarkening and darkening time properties. Selection of a cutoffwavelength may vary with the chromophore of the switching material,because the ring-open absorption spectrum and wavelength-dependence ofefficiency of ring-closing varies depending on chromophore structure.Where the cutoff filter blocks some or all of the incident UV light,and/or a portion of the higher energy visible light, the phostationarystate of the switching material may be altered—in some embodiments, thephotostationary state of the switching material may result in a lowerLT_(A) for the dark state than if the UV and/or higher energy visiblelight were not blocked.

Therefore, in some embodiments, control of the photostationary state byinclusion of a cutoff filter in the optical filter may be used tocontrol the appearance or color of the variable transmittance layer, andthus of the entire optical filter. By altering the amount of light belowabout 450 nm, or in the 540-600 nm range that is incident on thevariable transmittance layer, the equilibrium of ring open to ringclosed configurations of the chromophores may be shifted to increase ordecrease the proportion of molecules in the dark state, or ring-closedconfiguration.

Referring to FIG. 3, an embodiment is shown generally at 10. A variabletransmittance layer 14 may be disposed between a layer 12 and a colorbalancing layer 16. Layer 12 may be glass, and may be colored orcolorless. Layer 12 may function as, and may be referred to as, a firstlight attenuating layer. Surface 18 may additionally have a securityfilm layer disposed thereon to reduce scratching of surface 18 and/or toincrease the strength and toughness of the stack. Surface 20 may haveone or more additional layers disposed thereon, such as an anti-scratchlayer, an IR blocking layer, a self-cleaning layer or the like (FIG. 7b). An adhesive layer may be used to attach the variable transmittancelayer 14 or color balancing layer 16 to the layer 12 and/or the colorbalancing layer 16 to the variable transmittance layer 14. Examples ofan adhesive layer include a pressure sensitive adhesive (PSA) or anadhesive resin such as PVB, EVA, polyurethane, polyvinyl chloride,ionomer resin or the like. FIG. 6a illustrates an alternate embodimentwith a colored layer outboard to the VTOF layer 14—in this embodiment,the colored layer be a light attenuating layer.

Referring to FIG. 4, another embodiment is shown generally at 23. Thevariable transmittance layer 14 may be attached to the layer 12 with afirst adhesive layer 24, and to a second layer 28 by a second adhesivelayer 26. Second layer 28 may be a glass layer. In the embodiment shown,the color balancing layer 16 is attached to a side of the second layerof glass 28 opposite the second adhesive layer 26. In an alternateconfiguration, the color balancing layer may be attached to a side ofthe second layer by, within, or adjacent to, the second adhesive layer26.

FIG. 5 provides another embodiment of a laminated glass, illustratedgenerally at 30. The variable transmittance layer 14 may be attached tothe layer 12 with an adhesive layer 34, and to the second layer 28 witha second adhesive layer 32. Adhesive layers 32, 34 may be colored, orcomprise a colored layer—for example, adhesive layer 32 may comprise acolor balancing layer, and/or adhesive layer 34 may comprise an lightattenuating layer (incident light filter). Selection of thecolor/composition of layer 34 may be dependent on the particularphotochromic, or photochromic/electrochromic compound in layer 14, thecolor of layer 12 and/or 28, and/or on the composition of the incidentlight 22. Layers 32, 34 may of any suitable thickness from about 0.1 mmto about 1 mm, or any amount therebetween, for example 0.38 or 0.76 mm.

Another embodiment of the laminated glass of FIG. 5 further comprising asound insulating layer 36, and an infra-red (IR) blocking layer 38 isshown generally at 40 of FIG. 6. The illustrated configuration placeslayer 36 outboard of layer 38, however an alternate arrangement placinglayer 38 outboard of layer 36 is also contemplated (FIG. 7g ). FIG. 7hillustrates another layering configuration, placing layer 38 inboard oflayer 36 and the variable transmittance layer. A configuration placingan IR blocking layer 38 that absorbs IR light inboard of the variabletransmittance layer may be an advantageous configuration where it isdesirable to warm up the variable transmittance layer (e.g. when usingthe optical filter or laminated glass in a cold environment, operationof vehicles in cold climates or the like). FIG. 7i shows anotherembodiment where layer 12 may be a light attenuating layer and thespectra of the light attenuating layer may combine with the spectra ofthe variable transmittance layer to approximate a target color.Alternately, a color balancing layer aspect of a stack may be realizedby an adhesive layer or a layer of the variable transmittance layer(e.g. a tinted adhesive layer, or tinted substrate).

In another embodiment, an optical filter comprising a variabletransmittance layer may comprise connectors for connection to a controlcircuit. FIGS. 8a and 8b exemplify the layered compositions of FIGS. 7iand 7f , respectively, illustrating an optical filter comprising thevariable transmittance layer 14 connected to a control circuit; howeverit will be appreciated that any of the layered compositions comprising avariable transmittance layer with an electrochromic aspect may beconnected to this or a similar control circuit. Adhesive layers 24 and26 laminate the variable transmittance layer 14, or the variabletransmittance layer 14 and color balancing layer 16, between first 12and second 28 layers. The first 42 and second 44 electrical leadsconnect the variable transmittance layer to a control circuit comprisinga power source (voltage source) 46. A switch 48 may open and close thecontrol circuit to control power to the switchable optical filter basedon input. Switch 48 may be a two-way or three-way switch, or may be amulti-state control device such as a potentiostat, and allow selectionof different states of the variable transmittance layer. Input may comefrom a user (e.g. operation of a switch), or some other input such as atimer, pre-existing instructions (e.g. programmed into a memorycomprising part of the control circuit) a device monitoring the lighttransmittance of the switchable optical filter, incident light, and maybe operable by a user, a pre-existing program, timer or anothercomponent of the control circuit.

Other components of a control circuit may include a DC-DC converter forconverting the voltage from the power source to an appropriate voltage,a voltage regulator, timer, light sensor, voltage or resistance sensorsor the like. Control circuits and systems that may be used with variabletransmittance optical filters and layered compositions according tovarious embodiment are described in, for example, PCT publicationWO2010/142019, and U.S. Provisional patent application 61/625,855 filedApr. 18, 2012 (now International Application No. PCT/CA2013/000381).

Electrical leads 42, 44 and the variable transmittance layer 14 maytogether provide a physical separation between adhesive layers 24, 26.Alternately, electrical leads 42, 44 extend out one side of thelaminated glass (such as in FIG. 9), and layers 24, 26 are bonded aroundthe periphery of the variable transmittance layer, encapsulating thevariable transmittance layer 14, busbars 58 a, b and a portion of theelectrical leads 42, 44 contacting busbars 58 a, b, forming a sealedoptical filter.

FIGS. 9a and b shows a schematic diagram of a variable transmittancelayer, illustrating busbars and electrical leads connected thereto. Avariable transmittance optical filter comprising a layer of switchingmaterial 52 between first 54 and second 56 substrates is electricallyconnected to electrical leads 42, 44 via busbars 58 a, b applied to aconductive coating 60 a, 60 b on substrates 54, 56, in contact with theswitching material 52. The substrates of the switchable optical filterhave opposing overhanging edges, cut to expose the conductive coating.Peripheral seal 64 seals the cut edge of the switching material. The cutvariable transmittance optical filter may be attached to first 66 andsecond 68 transparent layers with adhesive layers 70 (before or afterapplication of the first seal material). Additional seal material 78 isapplied in a space defined in part by the first and second transparentlayers 66, 68 and the seal material 64. This additional seal materialmay be a separate application of the same substance as the first sealmaterial, or may be a different seal material.

Glass:

Where layers 12 and/or 28 are glass, they may independently be fromabout 1 mm to about 6 mm thick, or any amount therebetween—for example1.5, 2, 2.5, 3 mm or the like. Glass layers may independently be coatedwith, or comprise heat or infrared reflecting or absorbing materials, orUV reflecting or absorbing materials. Glass layers may independently bemineral glass (e.g. float glass, tempered glass or an organic glass; anorganic glass is an amorphous, solid glasslike material made oftransparent plastic. Organic glass may provide advantages such astoughness, reduced weight, improved thermal insulation, ease of colourmodification (incorporation of colorants in the plastic when molding) orthe like. Examples of organic glass include polycarbonate (e.g. LEXAN™),acrylonitrile butadiene styrene (ABS), polyesters (PET, PETG), acrylics(polymethyl methacrylate) (e.g. PLEXIGLAS™, LUCITE™) or modifiedacrylics (imidized, rubber toughened, stretched or the like), polyestercarbonate, allyl diglycol carbonate, polyether imide, polyether sulfone(polysulfone, PSU), cellulose acetate, cellulose butyrate, cellulosepropionate, polymethyl pentene, polyolefins, nylon, polyphenylsulfone,polyarylate, polystyrene, polycarbonate, polysulfone, polyurethane,polyvinyl chloride, styrene acrylonitrile (SAN), EVA, or the like.

Glass layers may independently be tinted. Examples of tinted glassinclude ‘grey’, ‘bronze’ or ‘green’ glass, and may be selected toachieve certain levels of light transmission (visible, UV or IR), or toharmonize with the site of installation e.g. exterior automotive paint,building envelope, or to harmonize with other components of a laminatedglass. Glass color may be described with reference to colour values L*a*and b*, and/or LT_(A). Grey glass may have an LT_(A) of about 9 to about63%, or any amount therebetween; an L* value of about 36 to about 84 orany amount therebetween; an a* value of about −2.5 to about 1.6 or anyamount therebetween; and a b* value of about −1.8 to about 3.6 or anyamount therebetween. Green glass may have an LT_(A) of about 52 to about91% or any amount therebetween. Green glass may have L* value of about78 to 97 or any amount therebetween; an a* value of about −11 to 0 orany amount therebetween; and a b* value of about −0.5 to about 1.5 orany amount therebetween. As examples, U.S. Pat. No. 5,308,805 describesa neutral low transmittance glass and U.S. Pat. No. 7,932,198 describesexamples of grey glass.

In some embodiments, the first glass layer 12 may be clear, or may begrey, with an LT_(A) of about 25-35% or any amount or rangetherebetween. The second layer of glass 28 may be clear, or may becolored (e.g. grey), with an LT_(A) of about 75-85% or any amount orrange therebetween. The layer 12 may be coloured to harmonize with theexterior paint of the vehicle or building where the laminated glass isinstalled, or to mask the inherent color of one or more layers in thelaminated glass (e.g. the variable transmittance layer, the staticfilter or the incident light filter, for embodiments where one or moreof these layers has a colour that does not harmonize with thesurrounding surface or paint). Alternately, the layer 12 may besubstantially clear to allow as much light as possible reach thevariable transmittance layer.

Where the glass is an organic glass, it may be advantageous to include alayer of plastic (e.g. PET film) between the organic glass and anadhesive layer or sound insulating layer comprising PVB, to preventdiffusion of plasticizers or other components of the adhesive layer intothe organic glass.

Variable Transmittance Layer:

A variable transmittance layer comprises a variable transmittanceoptical filter, itself comprising a switching material (switchablematerial). A variable transmittance optical filter comprises a first,and optionally a second, substantially transparent substrate, a firstand a second electrode disposed on the surface of at least one of thesubstrates and a switching material disposed between the first andsecond substrates, and in contact with the first and second electrodes.Examples of variable transmittance optical filters are described inWO2010/142019 and in provisional patent applications 61/589,153 and61/602,203 (now International Patent Application Nos PCT/CA2013/000054and PCT/CA2013/000176). Additional examples of switching material aredescribed in International patent application No. PCT/CA2012/000910. Thefirst, second or first and second substrates may be colorless or may becolored; in some embodiments, the color may be selected to becomplementary to that of the switching material in a dark state, fadedstate or dark state and faded state, and/or complementary to the colorof one or more layers in the optical filter or laminated glass

Switching Material:

Switching material disposed upon a substrate, with or without a secondsubstrate, may be generally referred to an optical filter. In someembodiments, the switching material may be disposed upon a firstsubstrate, or “sandwiched’ between a first substrate and a secondsubstrate, the switching material capable of transitioning between alight state and a dark state based on application of light in the UVand/or VIS range, and application of an electric voltage. The switchingmaterial may be a liquid, a gel, a solid or a semi-solid, and may beformed in a layer with a thickness of about 0.1 micron (micrometer, μm)to about 100 microns, or any amount or range therebetween, for examplefrom about 10 microns to about 50 microns, or from about 0.1 micron toabout 10 microns, or from about 0.5 micron to about 5 microns, or fromabout 0.5 micron to about 2.5 micron or any amount or rangetherebetween. In some embodiments, the layer of switching material is ofuniform, or substantially uniform, thickness. In some embodiments, thelayer of switching material is of non-uniform thickness.

A switchable film, or optical filter or device comprising a switchablefilm, may have a switching time from a dark state to a faded state offrom about 10 seconds to about 5 minutes, or any amount or rangetherebetween. Switching time may be altered by varying one or more ofthickness of material (e.g. a layer or cast sheet of switchingmaterial), solvent proportion, chromophore proportion, degree ofcrosslinking of the thermoset polymer, proportion of thermoset polymer,composition of thermoset polymer, hardness of the cross-linked switchingmaterial, or the like.

A switching material may have both electrochromic and photochromicproperties. A switching material may darken when exposed to ultraviolet(UV) light or blue light from a light source, and may fade when exposedto a voltage, or when exposed to light that excludes wavelengths belowabout 475 nm. Such a switching material may be alternately described asan auto-darkening material. In some embodiments, the switching materialmay fade upon exposure to selected wavelengths of visible (VIS) light,without sacrifice of the ability to be electrofaded when restored to adarkened state. In some embodiments, the switching material may darkenwhen exposed to light comprising wavelengths from about 350 nm to about450 nm, or any amount or range therebetween, and may fade when a voltageis applied. The switching material may be optically clear, ordemonstrate no more than 1%, no more than 2% or no more than 3% haze inboth faded and dark states.

Switching material, optical filters or laminated glass according tovarious embodiments may be described with reference to one or moreproperties, for example, photostationary state (PSS), photostability,visible light transmission (VLT), luminous transmittance (LT_(A))contrast ratio, colour, solubility, electrochemical durability, thermalstability, switching voltage, switching time, manufacturability,switching kinetics, haze, operating temperature, manufacturingconditions or processes or the like.

Switching material that may be used with optical filters is described inInternational patent application No. PCT/CA2013/000339 filed Apr. 9,2013, claiming priority to U.S. 61/621,736, filed Apr. 9, 2012, U.S.61/673,470, filed Jul. 19, 2012 and U.S. 61/706,001 filed Sep. 26, 2012.

A switching material may comprise (by weight percent) about 3 to about20 parts polymer or polymer matrix (e.g. a thermoset polymer), about 60to about 85 parts solvent, about 0.1 to about 10 parts ionic material(salt or the like), about 0.1 to about 30 parts of a compound havingelectrochromic and photochromic properties. The polymer matrix may beformed from crosslinking of a crosslinkable polymer. Generally (withoutwishing to be bound by theory), a switching material comprising agreater proportion of chromophore, solvent and/or ionic material mayhave a faster switching time than a switching material with a lesserproportion of chromophore, solvent and/or ionic material. A thinnerswitchable material may have a faster switching time than a thicker one.A switching material with a higher degree of cross-linking may have aslower switching time than one with a lesser degree of cross-linking. Aswitching material with a greater proportion of thermoset polymer,rheology modifier, or thermoset polymer and rheology modifier may have aslower switching time than one with a lesser proportion of thermosetpolymer, rheology modifier, or thermoset polymer and rheology modifier.A switching material may be applied to a substrate using extrusion orroll-to-roll coating, and a second substrate attached thereto, toprovide a variable transmittance filter.

An electrolyte is a conductive component of a switching material. Theconductive component may be a conductive liquid or other flowablematerial, or may comprise one or more solvents and one or more ionicmaterials (salt or the like). The electrolyte, or a solvent componentthereof, may have one or more of the following characteristics: aboiling point of about 150° C. or greater, a vapour pressure of about0.001 mmHg or less at 20° C., a Yellowness Index (YI) of about 6 orless; a flash point of about 80° C. or greater, a melting point of about40° C. or less. The solvent may be a plasticizer, or act as aplasticizer. A suitable solvent is compatible with components of aswitching material, and does not inhibit darkening or fading of theswitchable material; a suitable solvent may also demonstrate a suitablecyclic voltammetry profile (consistent reduction and oxidation peaks fortwo or more scan cycles), and/or suitable photostability (darkeningperformance of 90-100% of baseline for at least 250 hours of weathering,exposed to a light source providing 0.68 W/m² of UV light at awavelength of 340 nm—or about 0.6 MJ/m² cumulative exposure). Examplesof solvents include triglyme, tetraglyme, ethylene carbonate,butyrolactone, cyclopentanone, ethylene glycol phenyl ether; diethyleneglycol monobutyl ether, diethyl succinate; triethylene glycol di-2-ethylbutyrate (TEG DEB); tetramethylene sulfone (sulfolane);bis(2-ethylhexyl) adipate; Bis[2-(2-butoxyethoxy)ethyl] adipate (BEEA);triethylene glycol bis(2-ethylhexanoate) (TEG BEH); propylene carbonate(PC); 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (“Texanol”);diethyl azelate; dimethyl adipate (DMAd), diethyl adipate (DEAd),dibutyl itaconate (BI), 1,2-butylene carbonate, dibasic esters such asdimethyl 2-methylglutarate (Rhodiasolv IRIS™) or the like. In someembodiments, the solvent is optically clear, or substantially opticallyclear, and the one or more ionic materials, rheology modifiers, gellingagents, polymers, co-solvents, accelerants, hardeners, cross linkingagents and other components of a switching material or composition aresoluble in the solvent.

One or more solvents may be present in a switching material orcomposition in an amount from about 30% to about 95% (by weight), or anyamount or range therebetween, for example 30, 40, 50, 60, 70, 80 or 90%,or any amount or range therebetween. In some embodiments, the solvent,or one or more components of the solvent (e.g. where the solvent is amixture of two or more isomers or two or more compounds) may participatein a crosslinking reaction in the formulation. Such a solvent may bealternately referred to as a ‘reactive diluent’ or ‘reactive solvent’.

An electrolyte may comprise a salt. Examples of salts include alkalimetal salts, tetralkyl-, tetramethyl-, tetraethyl- or tetrabutylammoniumsalts, tetrabutylphosphonium salts, tetraphenylphosphonium salts,tributylmethylphosphonium salts or the like. Examples of salts includetetrabutylammonium tetrafluoroborate (TBABF₄), tetrabutylammoniumhexafluorophosphate (TBAPF₆) tetrabutylammoniumbis(trifluoromethanesulfonyl)imide (TBA-TFSI) or the like. The one ormore salts may be present in an amount from about 0.1% to about 10% (byweight) or any amount or range therebetween, for example 1, 2, 3, 4, 5,6, 7, 8, or 9%.

The polymer or polymer matrix may be a polyalcohol—examples includeethylene vinyl alcohol copolymer, polyvinyl alcohol (PVOH, PVAI),polyvinyl acetals (e.g. polyvinyl butyral, PVB), poly(ethylene oxide)(PEO), partially hydrolyzed EVA or the like. The resin may comprise alinear, branched, or dendrimeric polymer. Generally, a polyol resincombined with a crosslinking agent under suitable reaction conditionsmay crosslink two alcohol groups; crosslinking may be inter- orintra-molecular. Examples of crosslinking agents are known in the artand include, for example aldehyde (a di-, trialdehyde), an epoxide (adi-, tri- or poly epoxide, or “epoxy resin”), a mono, di- ortri-isocyanate crosslinking agent, a melamine resin, phenolic resins orthe like. A hardener may be used with some crosslinking agents. Forexample, an anhydride (e.g. MHHPA) may be used with an epoxy cure. Anaccelerant (catalyst) may be used to facilitate curing of the switchingmaterial.

Additionally, switching material or compositions according to variousembodiments may further comprise one or more other additives, such asdyes, UV light stabilizers, antioxidants, salts, surfactants, adhesionpromoters, charge carriers, charge compensators or the like.

Photochromic and Electrochromic Compounds (“Hybrid P/E” Compounds):

Examples of compounds having electrochromic and photochromic propertiesinclude hybrid P/E compounds. Hybrid P/E compounds are generallyorganic, and include classes of compounds from the hexatriene family(e.g. diarylethenes, dithienylcyclopentenes, and fulgides). Oxidation ofthe hybrid P/E compound to convert the ring-closed form to the ring-openform may be induced by application of a voltage to a switching materialcomprising the compound, and may be independent of the polarity of theapplied voltage. The hybrid P/E compound may be an anodic species, thatis, the electrochromic colour change (electrochromic fading,electrochromic transition from a dark state to a light state) occursprimarily at the anode of an electrochromic film or device.

Oxidative conditions are those where a compound according to variousembodiments undergoes a loss of an electron, at least transiently.Oxidation may occur with application of a voltage (electrochemicalconditions, or oxidative electrochemical conditions) or with theapplication of light from a light source (photochemical conditions).

Compounds according to various embodiments may undergo catalyticelectrochemical oxidation. The electrochemical conditions may becatalytic conditions, and compounds according to various embodiments mayundergo catalytic electrochemical oxidation. Catalytic electrochromismof selected diarylethenes has been demonstrated and is described in U.S.Pat. No. 7,777,050. The electrochemical conditions may be catalyticconditions and methods of switching, or operating, a switching materialfrom a dark to a faded state may employ application of a catalyticelectric charge. A catalytic amount of an electric charge may bepositive or negative, and may be from about 0 to about 5 volts, or anyamount or range therebetween. One or more hybrid P/E compounds may bepresent in a switching material in an amount (% weight) of about 0.05%to about 30%, or any amount or range therebetween, for example about 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24, 25, 26, 27, 28 or 29%.

Hybrid P/E compounds (1,2-diaryl cyclopentene compounds) reversiblyconvertible between a ring-open isomer and a ring-closed isomer aredescribed in U.S. Pat. No. 7,777,055, WO02010/142019 and PCT PublicationWO2013/044371. Some non-limiting examples of photochromic andelectrochromic diarylethene compounds include (for brevity, only thering-open isoform is shown):

Additional Layers

Transmission of light in the UV or IR may be blocked (by absorption orreflection) by one or more layers in the optical filter or laminatedglass. The optical filter or laminated glass may transmit some, all ornone of the incident UV light, or some all or none of the incident IRlight.

IR-Blocking:

One or more layers may comprising an IR-blocking component. A solarcontrol film may be included in the optical filter or laminated glass.Examples of such films include US 2004/0032658 and U.S. Pat. No.4,368,945. Alternately IR blocking materials may be incorporated into alayer of glass, or an adhesive layer. An IR blocking layer may reflector absorb IR light. Reflection of IR may reduce the solar heat gain ofan interior space, whereas absorption of IR may increase the temperatureof the laminated glass, which may be advantageous in increasing theswitching speed of the variable transmittance optical filter. Examplesof IR blocking layers include XIR 75 (Southwall), transparent metaloxides, “low-E” coatings or the like. In some embodiments, inclusion ofan IR blocking layer may reduce the temperature of the switchingmaterial. Reduction of the temperature of the switching material mayincrease the weathering performance of the switching material.

Uv-Blocking:

One or more layers may comprise a UV blocking component. Adhesive layerssuch as PVB may have additives that block UV (e.g. U.S. Pat. No.6,627,318); some transparent layers (e.g. layers 66 or 68), or somesubstrates (e.g. layers 54 or 56) may be made of a material that hasbeen treated with a UV blocking material (e.g. UV-blocking PET), or havea UV blocking layer applied thereto. It may be cost effective toincorporate into the variable transmittance optical filter a substratethat blocks UV—this may be advantageous in protecting the switchingmaterial from some incident UV light. Surprisingly, the variabletransmittance optical filter will still switch even when a UV blockingsubstrate that blocks 50% or more of incident UV light of 370 nm, 380nm, 400 nm, 420 nm, 435 nm or greater (a 50% cutoff filter). In someembodiments, the UV blocking layer may be, or comprise, PVB, or PET.

Sound Insulation:

Sound insulation may be provided by an acoustic layer. Acoustic PVB maybe known by trade names such as SAFLEX™ or VANCEVA™. U.S. Pat. No.5,190,826 describes composition comprising two or more layers of resinsof differing polyvinyl acetals; the acoustic layer may be in the rangeof 0.2 to 1.6 mm. U.S. Pat. No. 6,821,629 describes an acoustic layercomprising an acrylic polymer layer and polyester film layer. Acousticlayers comprising PVC, modified PVC, polyurethane or the like may alsobe used.

Self-Cleaning Coating:

a self-cleaning coating may be applied to an outboard surface of thelaminated glass, for example surface 20. Several examples of suchcoatings, and methods of applying them are known—examples includehydrophilic coatings based on TiO₂ (e.g. Pilkington ACTIV™) andhydrophobic coatings (e.g. AQUACLEAN™ or BIOCLEAN™)

Security Coating:

A security coating may be applied to the laminated glass to preventrelease of glass particles from laminated glass failure (breakage).Examples of such materials include PVB/PET composites or hard-coated PETfilms (e.g. SPALLSHIELD™ (DuPont).

Anti-Scratch:

An abrasion-resistant coating may be applied to the laminated glass toprevent distortion or surface damage, and preserve optical clarity;anti-scratch coatings may be particularly beneficial for use withorganic glass.

Coatings or treatments applied to the inboard or outboard surfaces oflaminated glass are generally optically clear. Other examples ofcoatings or treatments may include anti-glare or anti-reflectivecoatings.

Preparation of Optical Filters

Some methods of preparing optical filters and switching material aredescribed in WO2010/142019, and in International patent application No.PCT/CA2013/000339 filed Apr. 9, 2013. A switching material may be coatedat a suitable thickness onto a conductive coating of a substrate (e.g.ITO-coated PET) using a slot die, knife coater, roll-to-roll coatingmethod or the like. A second layer may be attached on the switchingmaterial—the second layer may be a transparent conductive layer, or asubstrate comprising a transparent conductive material (e.g. ITO coatedPET). The step of attaching the second layer may be preceded by, orfollowed by, a step of crosslinking or curing of the switching material.The step of curing may comprise heating the switching material to atemperature suitable for crosslinking (e.g. about 50 to about 90° C., orany amount or range therebetween. The step of disposing may be precededby a step of filtration.

Substrate

A substrate may be rigid or flexible—an optical filter comprising one ormore flexible substrate(s) may be in the form of a film that may beapplied to a rigid material, such as a pane of a window, or a lens. Asubstrate may comprise glass, plastics or thermoplastic polymers.Examples of glass include float glass, tempered glass, tinted glass,mirrored glass, reinforced glass, monolithic glass, multilayered glass,safety glass, bullet-resistant glass or “one-way” bullet-resistanceglass. Examples of thermoplastic polymers include polyesters (PE),polycarbonates, polyamides, polyurethanes, polyacrylonitriles,polyacrylacids, (e.g. poly(methacrylic acid), including polyethyleneterephthalate (PET), polyolefins (PO) or copolymers or heteropolymers ofany one or more of the above, or copolymers or blends of any one or moreof the above with poly(siloxane)s, poly(phosphazenes)s, or latex.Examples of polyesters include homopolymers or copolymers of aliphatic,semi-aromatic or aromatic monomeric units, for example polycondensed4-hydroxybenzoic acid and 6-hydroxynapthalene-2-carboxylic acid(VECTRAN™), polyethylene napthalate (PEN), polytrimethyleneterephthalate (PTT), polybutylene terephthalate (PBT), polyethyleneterephthalate (PET), polyhydroxyalkanoate (PHA), polyethylene adipate(PEA), polycaprolactone (PCL) polylactic acid (PLA), polyglycolic acid(PGA) or the like. Examples of polycarbonates include bisphenol A,polycarbonate or the like. Examples of thermoplastic polymers includepolyethene (PE), polypropylene (PP) and the like. The substrate may haveUV, IR or VIS light blocking characteristics. Other examples ofsubstrate materials include ceramic spinel or aluminum oxynitride.

The substrate may be of uniform or varying thickness, and of anysuitable dimension. For example, the substrate may have a thickness fromabout 0.01 mm to about 10 mm, or any amount or range therebetween, forexample 0.05, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 mm, or fromabout 0.012 mm to about 10 mm, or from about 0.5 mm to 10 mm, or fromabout 1 mm to 5 mm, or from about 0.024 mm to about 0.6 mm, or fromabout 0.051 mm (2 mil) to about 0.178 mm (7 mil). In some embodiments,the thickness and/or material of a first substrate differs from thethickness and/or material of a second substrate. In some embodiments, asubstrate with a conductive layer may be ITO-coated glass, or ITO-coatedPET.

In some embodiments, the substrate may be a moving web. The first and/orsecond substrates may be independently opaque or transparent, orsubstantially transparent. The substrate may be optically clear. In someembodiments, when the switching material is disposed upon, or sandwichedbetween the substrate(s), the switching material is optically clear(e.g. demonstrating a haze of less than about 5%, less than about 4%,less than about 3%, less than about 2% or less than about 1%). Haze maybe measured using methods known in the art, for example use of an XL-211Hazemeter from BYK-Gardner, according to manufacturer's instructions.

A transparent conductive layer (electrode) may comprise, for example,metals, metal alloys, metal oxides, conjugated organic polymers,conductive carbon-rich materials and fine wire meshes. Exemplaryconductive materials include layers of indium tin oxide (ITO), doped tinoxide, doped zinc oxide, doped cadmium oxide, fluorine tin oxide,antimony tin oxide, cubic strontium germanium oxide, polyaniline,graphene, fullerenes, carbon nanotubes, PEDOT(poly(3,4-ethylenedioxythiophene)), PEDOT:PSS(poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)), andpolypyrrole, as well as thin, substantially transparent metallic layerssuch as gold, silver, aluminum, and nickel alloy. Methods of applyingthe electrically conductive material to a substrate to form suitableconductive layers and electrodes are known, for example chemicaldeposition, sputter coating or the like. The conductive layer may be ofthickness that provides adequate conductance for operation of theelectrodes, and which does not appreciably interfere with thetransmission of light. The thickness of the conductive layer may be fromabout 1 nanometer to about 90 microns, or any amount or rangetherebetween. In some embodiments, a conductive material may bedissolved in a suitable solvent and cast in a layer (a transparentconductive layer), and used in a composite optical filter without beingapplied to a substrate. Such a layer may be of any suitable thickness,from about 0.05, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 mm or anyamount or range therebetween.

In some embodiments, the conductive transparent layer(s) may have asheet resistance of from about 100 Ohms/square to about 10,000,000Ohms/square; or any amount or range therebetween.

The switching material may have a high viscosity at room temperature andmay be made into a lower-viscosity liquid by heating to allow it to beapplied or coated onto the substrate. In one embodiment, the switchingmaterial is heated to about 100° C. and pressed between the substrates.Alternately, the switching material may be cast as a liquid and thenfurther treated to increase the viscosity of the material to form agel—the switching material may be dried (evaporation of a co-solvent),or a switching material comprising a crosslinkable resin may be cured toincrease the viscosity to form a gel. Curing the switching material maybe accomplished with temperature or UV light; other methods may besuitable with different formulations. This polymerization and/orcross-linking can be initiated by chemical-, thermal-, or photo-typeinitiators. The switching material may then adhere to conductive layerson first and second substrates to form an integral structure. In someembodiments, components of the switching material or composition may becombined in particular order, or in particular subcombinations(‘parts’), with the parts combined at a later point. Preparation offirst, second and/or third parts may be advantageous to solubilize oneor more components of a composition, prevent side reactions, or toprevent initiation of crosslinking (‘curing’) before the formulation iscomplete or ready for casting or coating. For example, a switchingmaterial for coating on a substrate may be prepared according to thesteps of: providing a first part comprising a crosslinkable polymer, ahybrid P/E compound, an ionic material and a first portion of a solvent;providing a second part comprising an optional hardener, a crosslinkingagent and a second portion of the solvent; providing an accelerant andan optional co-solvent (e.g. MEK, THF or the like); combining the firstpart and the second part; and combining the third part with the combinedfirst and second parts. Disposition of the switching material may beperformed in an environment of reduced oxygen (e.g. less than 100 ppm)and/or reduced humidity (e.g. less than 100 ppm relative humidity)

A suitable thickness may be selected such that the composition is of thedesired thickness once the co-solvent is evaporated (if the switchingmaterial comprises a co-solvent), or the final layer is of the desiredthickness following cooling and/or crosslinking of the coated switchingmaterial. For example, to obtain a final thickness of about 50 microns,a switching material with co-solvent may be applied to the substrate ina layer of about 100 to about 120 microns.

Once the filter has been made, it can be cut to size, sealed around theperimeter if necessary, and an electrical connection can be made to theelectrodes (conductive layers). The electrical connection can be made byprinting bus bars onto the substrates in contact with the transparentconductive coating. In some embodiments, busbars may be printed on thesubstrate before disposition of the switching material, or beforelamination of the substrate to the switching material. Electrical leads(electrical connectors, connectors) can then be attached to the busbars.

Busbars, Electrical Connectors and Control Circuits:

Busbars may be applied to a portion of the conductive layer on opposingsides of the switching material, so that a voltage differential iscreated across the switching material to effect the switch. The busbarsmay be of any suitable material to provide a low-profile conductive areasuitable for attachment of an electrical connector thereto. Examples ofsuitable materials include conductive adhesive, conductive ink,conductive epoxy, metal mesh or film or the like, comprising at leastone type of metal such as aluminum, gold, silver, copper or the like.The conductive material may be applied to the conductive surface by anyof several methods, including printing, painting, screenprinting(‘silkscreening’) or the like. Electrical connectors or leads may be ofany suitable material and may be affixed to the busbar by any suitablemethods, including adhesion (conductive adhesive or conductive epoxy),clips, rivets or the like. Suitable material for electrical connectorsmay include conductive tape, wire or the like.

A control circuit can be used to switch the electrical voltage on oroff, based on input from an automated or semi-automated device (e.g. anirradiance meter, thermometer), a building or vehicle environmentalcontrol system, a user or some other input, and can also be used tomodulate the voltage to a predetermined level. A power source for mayinclude an AC line voltage in a house or other building, a DC powersource (e.g. a battery of a vehicle, or in a separate battery or powerpack), an energy harvesting power source (e.g. solar panel) or the like.The control circuit may comprise one or more switches (transistor,relay, or electromechanical switch) for opening and closing a circuitbetween the voltage regulators and the optical filters, an AC-DC and/ora DC-DC converter for converting the voltage from the power source to anappropriate voltage; the control circuit may comprise a DC-DC regulatorfor regulation of the voltage. The control circuit can also comprise atimer and/or other circuitry elements for applying electric voltage tothe variable transmittance optical filter for a fixed period of timefollowing the receipt of input.

Embodiments include switches that can be activated manually orautomatically in response to predetermined conditions. For example,control electronics may process information such as time of day, ambientlight levels detected using a light sensor, user input, stored userpreferences, occupancy levels detected using a motion sensor, or thelike, or a combination thereof, the control electronics configured toactivate switches for applying voltage to the optical filter in responseto processed information in accordance with predetermined rules orconditions. Where the optical filter according to various embodiments ispart of an automotive glazing (window or sunroof, or the like), theglazing may be installed in the vehicle and electrically connected tothe vehicle's electrical system, through wiring in the frame, dash orroof, or connected to rails or guide tracks as may be used for someautomotive roof applications.

In one embodiment, the control electronics comprises a user-activatedswitch that passes the DC voltage from the power source substantiallydirectly to the variable transmittance optical filter. The useractivated switch can be a normally-open push button, or another type ofswitch. A switch may be configured to remain closed for a predeterminedamount of time following actuation, thereby facilitating application ofvoltage to the optical filter for sufficient time to effect a statetransition.

The voltage to be applied for transitioning the optical filter may befrom about 0.1 V to about 20 V, or any amount or range therebetween. Insome embodiments, the amount of voltage applied is from about 0.1V toabout 5V, or from about 1V to about 10 V, or from about 1.0 V to about2.2 V, or from about 0.5V to about 3V, or from about 1.2V to about 2.5V, or from about 1.8 V to about 2.1 V, or any amount or rangetherebetween. In some embodiments, the voltage applied is less thanabout 12 V, or less than about 6 V, or less than about 3 V or less thanabout 2.5 V, or about 2 V.

The variable transmittance layer may be laminated between layers ofglass.

Glass Lamination (for Weathering and Testing Devices):

In some embodiments, an optical filter comprising a variabletransmittance layer may be laminated between layers of glass. Once theswitchable film has been made, and busbars and optional electricalconnectors attached, this layer may be attached with an adhesive to asheet of glass, or laminated between two layers of an adhesive resin andthat between two sheets of glass. A “sandwich” ofglass-adhesive-switchable film-adhesive-glass may be placed in a Carverpress (Carver Inc. Wabash Ind.) and pressed at ˜55-90 psi at 135° C. for40 minutes, with ramp-up and cool down periods of about 10 minutes.

In another method, the sandwich may be placed in an evacuated bag,sealed to maintain the vacuum, and incubated in an oven with an initialbonding at a temperature of about 70° C.-110° C. An optional, secondbonding step may be performed at a temperature of about 120° C.-140° C.,with pressure (e.g. about 0.95 to about 1.5 MPa in an autoclave).

In another method, the sandwich may be passed through a press roll orpressed between plates at an elevated temperature (about 90° C. to about140° C.—pressure and temperature may be increased and decreased overseveral steps), or may be placed in a bag (rubber), with an initialbonding at a temperature of about 70° C.-110° C., while applying avacuum to remove air between the layers. A second bonding step is thenperformed at a temperature of about 120° C.-150° C., with pressure (e.g.about 0.95 to about 1.5 MPa in an autoclave).

The overall thickness of the laminated glass is dependent, in part onthe thickness of the various layers, generally an overall thickness ofabout 6.3 to about 6.6 mm is preferred. Performance of laminated glassor multi-layer compositions as described herein may be tested byconducting studies using standard techniques in the art, for example,measurement of VLT, LT_(A), color, haze, switching speed,photostability, and/or durability. WO2010/142019 describes methods,equipment and techniques that may be used to assess the performance ofoptical filters.

A laminated glass comprising an optical filter may be subjected totesting according to performance or safety standards. In someembodiments a laminated glass comprising an optical filter may meet orexceed the performance required by ANSI Z26.1, SAEJ673, ECE-R43, ANSIZ97.1, or similar performance standards in other jurisdictions.

The term “mil” as used herein, refers to the unit of length for 1/1000of an inch (0.001). One (1) mil is about 25 microns; such dimensions maybe used to describe the thickness of an optical filter or components ofan optical filter, according to some embodiments. One of skill in theart is able to interconvert a dimension in ‘mil’ to microns, and viceversa.

“About” as used herein when referring to a measurable value such as anamount, a temporal duration, and the like, is meant to encompassvariations of ±20% or ±10%, more preferably ±5%, even more preferably±1%, and still more preferably ±0.1% from the specified value, as suchvariations are appropriate to perform the disclosed methods.

Embodiments are illustrated, in part, by the following non-limitingmethods and examples:

General Methods

Preparation and Lamination of Variable Transmittance Layer:

Alpha 5 switching material comprising 2,2,4-Trimethyl-1,3-pentanediolmonoisobutyrate (Texanol™) (79.1 wt %). Butvar B72 PVB (8.5 wt %), DER736 (0.8 wt %/), MHHPA (0.7 wt %), AMC-2 (0.8 wt %), TBABF₄ (2 wt %) and10 wt % photo/electrochromic compound (S109 or S158) was prepared, andcombined 1:1 with co-solvent (MEK). This composition was coated on anITO-coated PET substrate to provide a final thickness of about 1-2 mil,the co-solvent evaporated and laminated with a second ITO-coated PETsubstrate and allowed to complete curing overnight at 80° C. The‘sandwich’ structure was cut to the desired size, sealed and electricalcontacts added.

Alpha 6.1 switching material comprising Texanol™ (76.79 wt %), ButvarB72 PVB (6 wt %), Desmodur N3600 (0.2 wt %), Zn Octoate (0.1 wt %),TBA-TFSI (2 wt %) and 15 wt % photo/electrochromic compound (S109 orS158) was prepared, and combined 1:1 with co-solvent (THF) for coatingand lamination as described for alpha 5 films.

Alpha 6.2 switching material comprising Texanol™ (65.27 wt %),1,2-butylene carbonate 11.52%, Butvar B72 PVB (6 wt %), Desmodur N3600(0.2 wt %), Zn Octoate (0.1 wt %), TBA-TFSI (2 wt %) and 15 wt %photo/electrochromic compound (S109 or S158) was prepared, and combined1:1 with co-solvent (THF) for coating and lamination as described foralpha 5 films.

Alpha 8.4i switching material comprising Rhodiasolv IRIS (68.76 wt %),Butvar B72 PVB (5 wt %), Mowitol B300HH (10 wt %) Desmodur N3600 (0.21wt %), Zn Octoate (0.04 wt %), TBA-TFSI (1 wt %) and 15 wt %photo/electrochromic compound (S109 or S158) was prepared, and combined1:1 with co-solvent (THF) for coating and lamination as described foralpha 5 films.

Glass Lamination:

Once the variable transmittance layer has been made, and busbars andoptional electrical connectors attached, this layer may be attached withan adhesive to a sheet of glass, or laminated between two layers of anadhesive resin and that between two sheets of glass. Laminated glassaccording to various embodiments of the invention may be produced in thesame production method as usual (non-switching) laminated glass. Theglass-interlayer sandwich may be passed through a press roll, pressedbetween plates at an elevated temperature (about 90° C. to about 140°C.—pressure and temperature may be increased and decreased over severalsteps), or may be placed in a bag (rubber), with an initial bonding at atemperature of about 70° C.-110° C., while applying a vacuum to removeair between the layers. A second bonding step is then performed at atemperature of about 120° C.-150° C., with pressure (e.g. about 0.95 toabout 1.5 MPa in an autoclave).

The overall thickness of the laminated glass is dependent, in part onthe thickness of the various layers, generally an overall thickness ofabout 6.3 to about 6.6 mm is preferred.

Assessment Methods:

Performance of optical filters or apparatus comprising an optical filtermay be tested by conducting studies using standard techniques in theart, for example, measurement of VLT, LT_(A), color, haze, switchingspeed, photostability, and/or durability. WO2010/142019 describesmethods, equipment and techniques that may be used to assess theperformance of optical filters.

Photochemical Darkening and Fading; Electrochemical Fading

Laminated glass or optical filters are exposed to UV light to darken theswitching material, resulting in a decrease in the light transmittanceof the material in the visible range. An electric charge of about 2Volts is then applied to the switching material for 3 minutes, causingthe switching material to switch to a faded state. In the faded state,more light is permitted to pass through the switching material resultingin an increase in light transmittance in the visible range. VLT orLT_(A) in both dark and faded states is measured using an Ocean Opticsspectrometer, and a contrast ratio may be calculated (LT_(A) fadedstate/LT_(A) dark state).

Photostability:

For photostability assessment, samples were prepared and weathered in aQSUN Weatherometer (Q-Labs) at 0.68 W/m². Devices were initiallydarkened on the QSUN for 1 hour and an initial dark state transmissionspectra obtained using an Ocean Optics spectrometer. Each device wassubsequently photo-faded using a low pressure sodium lamp with yellowfilter (400-500 nm cutoff), and an initial faded state transmissionspectra obtained. Devices were returned to the QSUN and spectra takentwice weekly until failure.

Photostationary State (PSS)

Absorption spectra over the visible range (380-780 nm) were obtainedusing an OceanOptics™ Spectrophotometer. A 2×10⁻⁵ M solution of compoundin solvent is prepared, and photofaded using visible light untilabsorption in the visible region of the spectrum stabilizes. The sampleis then irradiated with simulated sunlight (QSUN SS-150 Solar Simulatorwith xenon arc lamp) until the absorption spectrum stabilizes. To obtainPSS in the presence of a UV blocking film (if desired), a second sampleis prepared and irradiated as described, with a UV blocking filminserted in the light path when irradiating.

Film modeling: To obtain the scaled data for the film or film models,dark and light state absorption spectra were obtained using an OceanOptics spectrophotometer as described.

The array of absorbance data (cuvette) for each wavelength (380-780 nm)integer is multiplied by a scaling ratio (equation 2)

$\begin{matrix}{{\frac{{Path}_{cuvette} \times {{Conc}._{cuvette}}}{{MW}_{{chromophore}\mspace{11mu} I}} + \frac{{Path}_{film} \times {{Conc}._{film}}}{{MW}_{{chromophore}\mspace{11mu} I}}} = {{Scaling}\mspace{14mu}{ratio}}} & (2)\end{matrix}$

to provide an array of modeled film absorbance profile (equation 3):

$\begin{matrix}{{\begin{bmatrix}{{Abs}\; 380} \\\ldots \\{{Abs}\; 780}\end{bmatrix}\mspace{14mu}{cuvette} \times {Scaling}\mspace{14mu}{ratio}} = {\begin{bmatrix}{{Abs}\; 380} \\\ldots \\{{Abs}\; 780}\end{bmatrix}\mspace{14mu}{film}}} & (3)\end{matrix}$

The resulting array of the absorbance profile has a lambda max of thesame wavelength as the cuvette data.

In some embodiments, the film thickness (film path length, orPath_(film)) may be from about 0.5 mil to about 3 mil, or about 0.5,0.75, 1, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8 or 3. ChromophoreMW may be determined from the structure of the compound; concentrationof chromophore in the film may be of any suitable value.

Individual film spectra may be obtained from single films in both darkand faded states. For a dark state spectra, films were exposed tosimulated sunlight (Agro-Brite™ High output T5, 24 W/6400K fluorescentlamp, Hydrofarm Agricultural Products) until a stable dark state wasattained; for faded state, films were photofaded using a low-pressuresodium lamp (yellow light) until a stable faded state was attained.Transmission spectra were obtained using an Ocean Optics™spectrophotometer.

Example 1: Color Balance in Faded State

Light transmission spectra of a switching material comprising a compoundwith an observed green-blue color in the dark state and a pale yellow inthe faded state (S109) is shown in FIG. 1. In a faded state, about 80%LT_(A) is observed, and an LT_(A) of about 7% is observed for the darkstate.

FIG. 2 illustrates the transmission spectra for a ‘stack’ comprising theswitching material of FIG. 1 and a color balancing layer, providing anear neutral color in the faded state. For each component of a opticalfilter (color balancing layer, variable transmittance layer,light-attenuating layer, other layers and the like) a spectrum andL*a*b* values are obtained. The spectra for each component aremultiplied to provide a resultant spectrum, and resultant L*a*b* valuesderived from the resultant spectrum. In this manner, a variety of colorbalancing layer spectra and L*a*b* values may be substituted in themodeled resultant spectrum, to allow for comparison of the resultantL*a*b* values and allow selection of the combination of layers thatprovides a closest match to the target color in the dark or faded state(for this example, the target color is a neutral grey color in the fadedstate).

For the spectra illustrated in FIG. 2, the color balance layer selectedwas GamColor 970. Transmission peaks in the 430-490 nm and 550-640 nmranges have been altered to have a similar magnitude. While the lighttransmission over the illustrated range (380 nm to 780 nm inclusive) isnot equal, the resulting transmitted light is neutral, having a* and b*values near zero. Thus, it is not required to have a uniform levelspectrum in a variable transmittance optical filter of an opticalfilter, or laminated glass to achieve a neutral color.

Example 2: Color Comparison of Switchable Material in Faded or DarkState

Laminated glass stacks were mathematically modeled to examine the scopeof matching switching materials to a target color. For example, to matcha ‘grey glass’ with an L*a*b* of 41.7, −2.7, 3.9 and an LT_(A) of 12.4was selected as the target color and compared to switchable material inthe dark or faded state of the switchable material; a color balancinglayer was included in the predicted layer configurations (“stack”) tomodel the desired colour neutralization to match the grey glass in adark or faded state for the indicated chromophore. All switchingmaterials were modeled for a film thickness of 25 μm and chromophoreloading of 10 wt %. Information concerning the modeled laminated glasscomprising a variable transmittance layer is provided in Table 1.

TABLE 1 L*a*b*, delta C (comparing target color to stack color) anddelta E (comparing target color to stack color) values of modelledstacks comprising S109 or S158 hybrid photo/electrochromic compounds indark or faded state. Match to Match to faded state dark state 10 11 1415 delta C 0 0 0 0.3 (target to stack) delta E 0 0.1 0 0.5 (target tostack) chromophore S158 S109 S158 S109 faded state 90.8, 92.0, 90.8,92.0, (L*a*b*) −15.1, −10.2, −15.1, −10.2, 38.3 21 38.3 21 dark state68.2, 62.4, 68.2, 62.4, (L*a*b*) −50.8, −52.8, −50.8, −52.8, 7 −7.1 7−7.1 faded stack 41.7, 41.7, 63.8, 75.5, (L*a*b*) −2.7, −2.7, 31.3,35.8, 3.9 3.9 32.9 35.1 dark stack 29.5, 25.5, 41.7, 41.5, (L*a*b*)−17.7, −23.3, −2.7, −3.1, −8.9 −6.4 3.9 3.9 LT_(A) range 4.9-12.43.5-12.4 12.4-40.4 12.3-61.2 (dark-light) contrast ratio 2.5 3.5 3.3 5

Color Matching to a Faded State:

Both chromophores exhibit varying degree of yellow-tinge in the fadedstate, thus a color balancing layer with a blue component was modelledto manipulate the transmitted light to achieve a grey color in thetarget range. Light transmission of stacks for both chromophores wasable to be manipulated to provide a suitable grey color in the fadedstate (delta C of less than 10, and a VLT in the faded state of at least10%). In the dark state, S109 and S158 exhibited a suitable darkblue-green color. The delta C values for these samples indicate that thetarget color range was attained.

Color Matching to a Dark State:

the observed color of switching materials comprising S109 or S158 in adark state may be describe as blue-green. When color matching to a darkstate, a delta C of less than 10, along with an LT_(A) of 10% or more inthe dark state was considered to be suitable. Chromophores S158 and S109(blue-green in their dark state) were measured, and a color balancinglayer with a pink color component was used to manipulate the transmittedlight to achieve a grey color in the target range. The deltaC values forthese samples indicate that the target color range may be attained, withthe faded states providing a grey-orange color.

These results demonstrate that matching a target color within aspecified range and/or LT_(A) can be predicted for a variety ofswitching materials. Suitability of a particular match in the faded ordark state with a target color or range may be dependent on the intendeduse of the laminated glass or optical filter.

Example 3: Matching a Non-Neutral Color

A laminated glass with a blue dark state (L*=32.5, a*=−20.8, b*=−17.2,and neutral in the faded state) and an LT_(A) of about 2-26% wasselected as the target colors (targeted to match in both faded and darkstates. Laminated glass with a blue switchable region may be produced byinclusion of an optical filter comprising a variable transmittance layerand a color balancing layer. Information regarding the proposed colorand characteristics is provided in Table 2.

TABLE 2 Switchable material descriptors parameter delta C (target tostack) 18 delta E (target to stack)   19.8 chromophore S109 wt % 15%film thickness 1.5 mil faded state (L*a*b*) 91.2, −13.2, 33.1 dark state(L*a*b*) 41, −65.3, −14.8 faded stack (L*a*b*) 58.1, −0.5, 0.2 darkstack (L*a*b*) 25.6, −39.8, −21.7 LT_(A) range (dark-light) 2.3-25.8(LT_(A)) LT_(A) contrast ratio 11In this example, the color in the dark and the faded states are close tothe target colors of a blue in the dark state, and a neutral color inthe faded state.

Example 4: Effect of Film Thickness and/or Chromophore Load on ContrastRatio of Optical Filters

Chromophore loading and thickness of cast films were modeled toinvestigate the contrast ratio of various laminated glass compositions.LT_(A) values for laminated glass compositions comprising a switchingmaterial of varying thickness and chromophore loading were determined.The laminated glass composition comprised a switchable optical filtercomprising chromophore S109 and a static filter selected such that thefaded stack most closely matched a target spectrum having a neutralcolor and an LT_(A) of 37% in the faded state. Tables 3 and 4 set outthe LT_(A) in dark and faded, states respectively, for a range ofthickness and S109 wt %; Table 5 sets out the contrast ratio of thelaminated glass compositions.

TABLE 3 LT_(A) in dark states for films of varying thickness andchromophore load film thickness wt % 0.5 1 1.5 2 2.5 5 34.9 20.9 15 8.56.6 7.5 29.3 15 7.7 4.6 3.5 10 20.9 8.7 4.5 3 2.3 12.5 14.6 5.1 2.4 1.51.1 15 12 3.4 1.8 1 0.6 17.5 10.9 2.9 1.6 0.8 0.5 20 7.2 2.4 1.1 0.6 0.2

TABLE 4 LT_(A) in faded states for films of varying thickness andchromophore load film thickness wt % 0.5 1 1.5 2 2.5 5 50.6 43.1 42.232.8 32.7 7.5 50.6 42.3 32.8 29.9 25.9 10 43.1 32.7 25.8 25.8 25.8 12.543.1 32.7 25.9 25.7 19.6 15 42.3 29.9 25.8 19.6 19.5 17.5 42.1 25.8 25.519.4 19.2 20 32.8 25.7 19.5 19.3 14.2

TABLE 5 Contrast ratios film thickness wt % 0.5 1 1.5 2 2.5 5 1.4 2.1 2.8  3.9  5.0 7.5 1.7 2.8  4.3  6.5  7.4 10 2.1 3.8  5.7  8.6 11.2 12.53.0 6.4 10.8 17.1 17.8 15 3.5 8.8 14.3 19.6 32.5 17.5 3.9 8.9 15.9 24.338.4 20 4.6 10.7  17.7 32.2 71.0

A range of contrast ratios can be provided by varying chromophoreloading, film thickness or both. A contrast ratio of 8 or greater may beobtained in a laminated glass composition having at least 10%chromophore load, and/or at least a 1 mil thick.

Example 5: Attenuation of Incident Light

Light incident on the variable transmittance layer may be selectivelyattenuated by placing a filter outboard of the variable transmittancelayer. This light attenuation layer may be selected to address, forexample, photostability, durability or kinetics of the switchingmaterial, and may also affect the contrast ratio of the transmittedlight.

Light attenuation layers were applied to variable transmittance layerscomprising S109 and the effect of this layer on light transmission andcontrast ratio considered when darkening under artificial sunlight(QSUN) and electrofading in the presence (EF in QSUN) or absence (EF) ofartificial sunlight. Table 6 summarizes the results of adding thesefilters atop the formulation including the color, contrast ratio (CR),and LT_(A) in both dark (in QSUN) and faded (EF) state for both neutralcolor matching in the faded state and not. FIG. 11 shows lighttransmission spectra for each of the four filters, exemplifying thewidely varying spectra that may be employed for selective manipulationof optical filter spectra to approximate a target color.

TABLE 6 effect of light attenuation layer on light transmission andcontrast ratio. Color Matched Filter QSUN EF in QSUN EF CR LTA NoneL*a*b* 50.5, 67.3, 90.5, 6.1 4.3-26.3 −62.5, −48.8, −12.6, −13.7 3.129.8 LT_(A)/CR 11.9 30.0/2.5 78.5/6.6 7 L*a*b* 53.5, 68.2, 85.1, 44.4-17.7 −56.9, −37.2, −11, 1.5 19 40 LT_(A)/CR 15.7 34.3/2.2 68.6/4.41543 L*a*b* 42.3, 56.5, 68.4, 3.3 0.7-2.3  −34.4, −6.5, 15.7, 16.3 36.954.6 LT_(A)/CR 10.8 25.7/2.4   45/4.2 4390 L*a*b* 38.3, 52.7, 63.8, 6.40.7-4.5  −62.2, −61.9, −53.7, −13.2 0.3 10.2 LT_(A)/CR 5.8 14.8/2.626.4/4.6 398 L*a*b* 34.7, 50.3, 61.9, 5.4 1.9-10.2 −46.7, −30.3, −11.6,−8.1 8.5 22.2 LT_(A)/CR 5.5 16.3/3.0 30.4/5.6

Rosco 07 Pale Yellow: Photostability of chromophores may be improved iflight in the UV wavelength region is attenuated. This filter provides alayer that attenuates light below about 400 nm in these wavelengths theformulation will not darken, resulting in the choice of allowing 50% ofUV and short wavelength light below 400 nm and as much as light aspossible thereafter. Chromophores may also switch to a dark state whenstimulated with light in the ˜400-420 range.

GamColor 1543 Full CTO: This filter provides a layer that attenuates alllight up to about 650 nm to about 50%, and allows maximum transmissionof incident light above ˜650 nm, thus reducing the quantity of higherenergy wavelengths incident on the switching material. By reducing theamount of light incident on the switching material, photostability maybe improved, while maintaining LT_(A) as high as possible.

Rosco 4390 CalColor 90 Cyan: Photofading is observed with somechromophores—or switching material comprising same—when exposed to lightaround ˜650 nm. This filter has an absorption spectrum comprising aGaussian shape with a half-height width of around 200 nm, centered about650 nm. By attenuating light in this region of the spectrum, thephotostationary state of the chromophore may be improved (a darker darkstate) by preventing the photofading that occurs due to the S109chromophore also having an absorption peak centred around 650 nm.Conversely, attenuation of light in this region may also aberrantlyaffect fading of switching material by reducing any photofading effect,and making the fading reaction more reliant on electrofading alone.

Rosco 398 Neutral Grey: This filter provides a layer that attenuates alllight in the visible range, and has an LT_(A) of 39%. This overallattenuation of incident light reduces the higher energy wavelengths,thus may improve photostability and/or durability of the switchingmaterial. By reduction of the overall light incident on the variabletransmittance layer, overall light transmission is reduced, providing alower LT_(A) for a laminated glass or optical filter comprising such alayer.

Example 6: Color Balance Layer Calculation

A custom color balance layer having a spectrum with min/max bounds forLT_(A) of 0 and 85% respectively was modeled in a optical filter with avariable transmittance layer comprising S109 (S109 spectrum illustratedin FIG. 1). The model was presented with the following parameters:LT_(A) in the dark state of 1% and a neutral color in the faded state.Absorption peaks were iteratively introduced into the spectrum of thecustom color balance layer to improve contrast ratio between dark andfaded state, while maintaining the parameters. FIG. 12 shows acalculated custom spectrum of an optical filter comprising S109 and acustom color balance layer in the dark (solid line) and faded (dottedline) states; the spectrum of the modeled color balance layer isindicated by the alternating dot-dashed line. The resulting contrastratio of the optical filter was 25.7 with an LT_(A) in the dark state of1% and LT_(A) in the faded state of 25.7%. The L*a*b* of the dark stateis 12, 14.1, −33.4 and for the faded state 55.9, 3.0, 3.0. The firstpeak located in the ˜540-590 nm region provides for an improved contrastratio due to the large spectrum difference between dark and faded statesof the S109 variable transmittance layer. The peak located in the˜380-470 nm region is selected to complement the first peak and providea neutral faded state.

This model demonstrates that it is possible to introduce additionalabsorption peaks may be introduced in the color balance layer in the˜500-550 nm region and/or the ˜650-780 nm region may be introducedwithout sacrificing color neutrality in the faded state.

Example 7: Temperature and Glazing Sample Configuration

Switching material (alpha 6.1) in films encapsulated with a thermocouplewere placed in a QSUN weathering chamber for 30 minutes, calibrated toblack panel temperature of 70° C. The films were overlaid with tintedglass (GREYLITE™) or overlaid with GREYLITE and an infrared (IR)blocking layer (XIR 75 from Southwall). Differences in devicetemperature were observed—inclusion of tinted glass increased thetemperature of the film (68° C.), compared to 63.6° C. for a film withGREYLITE and the IR blocking layer (63.2° C.). Inclusion of GREYLITE ina multilayer glazing may provide, at least in part, a neutral color, butwithout an IR blocking layer, the temperature of the switching materialincreases.

Example 8: Temperature and Glazing Sample Configuration

Seven ‘stack’ configurations comprising a variable transmittance layerand laminated with a thermocouple inboard of the variable transmittancelayer. The stacks were exposed to simulated sunlight (Solar Simulator),and the temperature logged over several minutes until stabilized. Thecomposition of the variable transmittance layer is illustrated in FIG.13. Layer 128 a: 100-PET (Melinex 454); 102—pressure sensitive adhesive(PSA 8172); 104—ITO-coated PET (ST504) with ITO coating facing 106; 106switchable material alpha 6.2. Layer 128 b has a layer of XIR72-41.Layer 128 c has a layer of Gamin 1514 film (grey PET film).

The slack configurations (Stacks A-G) are shown in FIG. 13, numberedcomponents are set out in Table 7. Stacks A and B are the same, butinvert the IR blocking layer 124 a/b. Stacks D and E are the same, butwith the IR blocking layer 124 a/b incorporated into the variabletransmittance layer (in place of one of the PET layers 100).

TABLE 7 Number Component 120 Grey glass - SolarGrey glass 3 mm 122Pressure sensitive adhesive - PSA 8172 124a IR blocking layer - XIR72-41IR layer facing away from 128 124b IR blocking layer - XIR72-41 IR layerfacing towards 128 126 BGR15 PVB 128a Variable transmittance layer 128bVariable transmittance layer with 124a (outboard of switching material)128c Variable transmittance layer with 124b (outboard of switchingmaterial) 128d Variable transmittance layer with 136 (outboard ofswitching material) 130 Thermocouple 134 Clear glass 136 GAM 1514 (greyPET) 138 Clear glass with low-E soft coat (Solarban 70)

FIG. 14 shows the temperature of each device over time when under theSolar simulator. The temperature profiles of the stacks A-G segregategenerally into two groups—those with low-E coatings (stacks C and F),and those with XIR layers (stacks A, B, D and F) or control (stack G).None of the stacks comprises an air gap or evacuated space, and the lowE coating on the glass in stacks C and F were internal to the stacks(the low-E coating faced the interior of stack F). These resultsdemonstrate the ability of some infrared blocking layers tosignificantly influence the temperature of the interior of the stack,and thus the temperature of the switching material.

Example 9: Temperature and Fading Time

An optical filter with GreyLite II, comprising an alpha 8.4i switchingmaterial was prepared, darkened using a solar simulator (to about 2%LT_(A)), and electrofaded while maintained at 23° C., 40° C. or 60° C.(2 volts, 10 second polarity reversing cycle). Time in seconds to reach50% PSS (11.2% LT_(A)), 10% PSS (82.5% LT_(A)), or transition from 90 to10% PSS (19% LT_(A) to 3.5% LT_(A)) for each temperature is set out inTable 8. The rate of electrofading increased with an increase intemperature.

TABLE 8 23° C. 40° C. 60° C. 50% PSS (11.2) 40 27 19 10% PSS (19) 82.557 34.5 90to10% PSS (3.5 to 19) 73 52 28.5

Example 10: Weathering of Test Devices at Different Temperatures

Test devices comprising 10 wt % S158 in Texanol in a glass weatheringcell (50 micron thickness) were placed in a QSUN weathering chambercalibrated to a black panel temperature of 50° C., and darkeningperformance assessed over exposure (MJ/m² at 340 nm). After 3.1 MJ/m² ofexposure, the QSUN temperature was increased to 70° C. black paneltemperature, and darkening performance assessed over exposure. Percentof initial darkening performance is calculated according to equation(4):

$\begin{matrix}{{\%\mspace{14mu}{of}\mspace{14mu}{initial}\mspace{14mu}{darkening}} = {\frac{{\%\mspace{14mu} T_{{light}\mspace{11mu} o}^{\lambda}} - {\%\mspace{14mu} T_{{dark}\mspace{11mu} i}^{\lambda}}}{{\%\mspace{14mu} T_{{light}\mspace{14mu} o}^{\lambda}} - {\%\mspace{14mu} T_{{dark}\mspace{14mu} i}^{\lambda}}} \times 100\%}} & (4)\end{matrix}$

For samples at the initial timepoint (0) and for subsequent timepoints iTransmission spectra (380-780 nm) are obtained for each device in darkand faded states initially (timepoint 0) for subsequent timepoints i for% transmission (% T) in the faded (light) and dark states. Transmissionat wavelength λ is used for each calculation—λ is selected as thewavelength with 10% transmission in the initial dark state, determinedfor each device—the same λ is used for each subsequent determination of% of initial darkening. Dark state is measured on the device as it isremoved from the QSUN. A faded state is achieved by irradiating thesample with a low pressure sodium lamp.

FIG. 15 illustrates the rate of change of darkening from the initialstate for devices held at 50° C. and 70° C. Samples held at elevatedtemperature demonstrate an accelerated rate of degradation (as measuredby a decrease in the darkening performance over exposure).

The weathering performance of test devices is shown to decrease atelevated temperature.

Example 11: Weathering Performance of Test Devices with UV Blockers

Higher energy light (including higher energy VIS and UV light) darkensswitching materials. PVB laminated test specimens (devices) with alpha6.1f formulation were placed in a QSUN weathering chamber calibrated toa black panel temperature of 70° C. FIGS. 16A, B show the weatheringperformance of devices comprising various UV blocking layers with 390,400 or 420 nm cutoff wavelength (blocking 50% or more of wavelengthsbelow the cutoff). Darkening performance decreases significantly fasterfor samples with a UV blocking layer having a lower cutoff wavelength,and blocking of higher energy light increases the darkening performanceover time. Surprisingly, samples continued to darken even with a 400 nmor 420 nm cutoff filter. Because the chromophores used in the testdevice were initially believed to require UV light to darken, it wasunexpected that photoactivated darkening is maintained even whenblocking light up to 420 nm.

Example 12: UV Cutoff Filters, Darkening Time and Photostationary Stateof Variable Transmittance Optical Filters

Studies were performed on a 1.2 mil (unlaminated) film with aformulation containing 15% S158, 10% Mowitol B60HH, 3% Butvar B72, 0.35%hexamethylene diisocyanate, 0.01% ZnOct, 1% TBATFSI, 63.64% diethylsuccinate, and 7% 1,2-butylene carbonate. The film was coated onto asheet of ST504 using a 4 mil gap. The film was faded for 3 minutes withvisible light from a low-pressure sodium lamp, then positioned on astage and exposed continuously to simulated sunlight. Transmissionspectra recorded at 0.5 s intervals using an Ocean Optics detectorpositioned beneath a hole in the stage, opposite the Solar Simulatorlight source, with or without cutoff filters positioned between thelight source and the film. Spectra were recorded until fluctuations inthe transmission measurements were no longer significant. Cutoff filters(50%+/−6 nm): 370 nm, 400 nm, 420 nm, 435 nm and a 455 nm. Table 9 setsout the L*a*b* (comma separated values) in the dark and faded states,and LT_(A) at the dark (PSS) faded and intermediary states for eachoptical filter comprising the S158 switching material and cutoff filteras indicated. With increasing blocking of the UV and higher energyvisible wavelengths, the ability of the film to achieve a fully darkstate is not hindered until the 455 run filter is applied. Withinclusion of the 455 nm filter, the equilibrium between ring-open andring closed states of the chromophore in the switching material isshifted, and a prominent change in the b* value is observed. The lighttransmittance at 10, 50 or 90% PSS does not differ greatly for samples1-5, however an increase in the light transmittance at 90% PSS (lessabsorbance) is noted for sample 6. The time to transition (90-10% PSS)increases with blocking of longer wavelength light.

TABLE 9 Characterization of test samples with or without selected cutofffilters. Test Sample 1 2 3 4 5 6 Filter no 370 400 420 435 455 filter nmnm nm nm nm Faded LT_(A) 71.5 71.5 71.5 71.5 71.5 71.5 (0% PSS) L*a*b*faded 87.3, 82.6, 84.3, 86.8, 85.8, 86.9, −23.2, −25.9, −22.3, −17,−17.4, −17.5, 64.7 57.2 60.8 71.2 66.6 72.4 Dark LT_(A) 11.8 12.9 13.313.7 14.4 20.0 (100% PSS) L*a*b* dark 48.8, 49.9, 50.4, 50.6, 51.5,57.2, −74.9, −70, −69.5, −68.7, −67.8, −64.7, 9.1 9.9 11.7 14.2 15 27LT_(A) 41.6 42.2 42.4 42.6 42.9 45.7 at 50% PSS LT_(A) 65.5 65.6 65.665.7 65.7 66.3 at 10% PSS LT_(A) 17.8 18.7 19.1 19.5 20.1 25.1 at 90%PSS Time (seconds) 3 3 4 5 5.5 8 to 50% PSS Time (seconds) 19.5 24.527.5 32 35.5 43 90-10% PSS

TABLE 10 Time (seconds) for test samples 2-6 to achieve 50% PSS ortransition from 90%-10-% PSS of Sample 1. Test sample 1 2 3 4 5 6 Filterno 370 400 420 435 455 filter nm nm nm nm nm Time to 50% 3 3.5 4 5.5 611 PSS of #1 (no filter) Time to 90-10% 19.5 27 33 40.5 50 N/A PSS of noFilter

Table 10 sets out the time for the test samples 2-6 to achieve the 50%PSS of sample 1, and the time to transition from 90% to 10% PSS of theunfiltered sample (sample 1). With blocking of longer wavelength light,the time to attain the same PSS as a film with no filter increasessubstantially, and for test sample 6, the PSS can't be reached.

These data demonstrate that the light transmittance of the dark state ofan optical filter, and the transition time of an optical filter, can beadjusted, at least in part, by selective blocking of longer wavelengthUV light, shorter wavelength visible light, or both.

FIG. 17 shows a ring-open absorption curve for S158, overlaid with thetransmission curves for the cutoff filters. Light of lower energy(higher wavelength) than the indicated cutoff wavelength of the filtersshown (non-filtered light) is able to darken a film containingchromophore S158 despite the very low absorbance at these unfilteredwavelengths relative to the absorbance at lambda max of S158 (335nm—absorbance peak of solid black line in FIG. 17), and has very littleeffect on the dark state achieved. FIG. 18 shows, surprisingly, thatextent of darkening is not significantly reduced by the use of cutofffilters of 435 nm or below, but darkening time is increased (FIG. 19with filters of increasing cutoff wavelength above 370 nm. Light filterswith higher cutoff wavelengths may decrease the amount of the S158ring-closed isomer present at the photostationary state (PSS) andincrease the time required to reach the PSS.

Example 13: Impact Testing

Impact testing according to ANSI Z26.1 was conducted—a 27 g ball dropfrom 10 m (30 ft), a 227 g dart drop from 10 m (30 ft), and a 2.26 kgball drop from 4 m (13 ft). The three drop tests were performed onlaminated 30 cm×30 cm samples containing as a variable transmittancelayer a film with alpha 5 switching medium, and layers according toStack F, absent the thermocouple, and substituting clear glass for theSolarGrey. Samples were laminated using a Carver press, or in anautoclave. In none of the tests did the ball or dart pass through any ofthe samples. No large pieces detached from any of the samples. All thesamples tested passed the impact tests according to the regulations.

Example 14: Boil Testing

Boil testing according to ANSI Z26.1 was conducted on 100×100 mmlaminated glass samples, containing as a variable transmittance layer afilm with alpha 5 switching medium, and layers according to Stack F,absent the thermocouple, and substituting clear glass for the SolarGrey.Samples were laminated using a Carver press, or in an autoclave. Theability to electrofade samples from 90% PSS to 10%0 PSS before, andafter boil testing was unaffected with boiling, and LT_(A) remainedunaffected (Table 11).

TABLE 11 Faded LT_(A) Dark LT_(A) Before Boil Test 75.8 7.2 After BoilTest 75.8 6.6

Example 15: Optical Filter for an Automotive Glazing

In an embodiment where an optical filter is used in an automotiveglazing, it may be desirable to maximize weathering durability andcontrast ratio while minimizing LT_(A) in the dark state, and minimizingthe time to fade with constant sunlight exposure. For an optical filtercomprising a switching material with chromophore S158, a UV blockinglayer with UV cutoff wavelength of 435 nm may be selected. Such anoptical filter has been demonstrated to show no significantdeterioration in the dark state LT_(A) achieved (Example 12 and FIG.18), and darkening time is maximized (Example 12 and FIG. 19). A minimaltime for electrofading is preserved, and the filtering of more UV lightand higher energy visible light improves the weathering performance(Example 11 and FIGS. 16A and 16B), which allows for faster fading inthe presence of sunlight due to the competition in darkening kineticsand electrofading kinetics or net fading kinetics or fading occurs to agreater extent in examples where incomplete fading occurs in thepresence of sunlight due to the described kinetics competition.

OTHER EMBODIMENTS

It is contemplated that any embodiment discussed in this specificationcan be implemented or combined with respect to any other embodiment,method, composition or aspect, and vice versa.

The present invention has been described with regard to one or moreembodiments. However, it will be apparent to persons skilled in the artthat a number of variations and modifications can be made withoutdeparting from the scope of the invention as defined in the claims.Therefore, although various embodiments of the invention are disclosedherein, many adaptations and modifications may be made within the scopeof the invention in accordance with the common general knowledge ofthose skilled in this art. Such modifications include the substitutionof known equivalents for any aspect of the invention in order to achievethe same result in substantially the same way. Numeric ranges areinclusive of the numbers defining the range. In the specification, theword “comprising” is used as an open-ended term, substantiallyequivalent to the phrase “including, but not limited to,” and the word“comprises” has a corresponding meaning. As used herein, the singularforms “a”, “an” and “the” include plural referents unless the contextclearly dictates otherwise. Citation of references herein shall not beconstrued as an admission that such references are prior art to thepresent invention, nor as any admission as to the contents or date ofthe references. All publications are incorporated herein by reference asif each individual publication was specifically and individuallyindicated to be incorporated by reference herein and as though fully setforth herein. The invention includes all embodiments and variationssubstantially as hereinbefore described and with reference to theexamples and drawings.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as is commonly understood by one of ordinary skillin the art to which this invention belongs. If a definition set forth inthis section is contrary to or otherwise inconsistent with a definitionset forth in the documents that are herein incorporated by reference,the definition set forth herein prevails over the definition that isincorporated herein by reference.

What is claimed is:
 1. An optical filter comprising: a variabletransmittance layer having a first spectrum in a dark state and a secondspectrum in a faded state, wherein each of the first and second spectracomprise a visible portion; an infrared (IR) blocking layer, wherein thevariable transmittance layer and the infrared (IR) blocking layercomprise a stack; and a color balancing layer having a third spectrumand comprising part of the stack, wherein the third spectrum comprises avisible portion, the first and third spectra combine to provide a darkstate spectrum approximating a dark state target color, and the secondand third spectra combine to provide a faded state spectrumapproximating a faded state target color.
 2. The optical filter of claim1 wherein the variable transmittance layer comprises a switchingmaterial transitionable from a faded state to a dark state when exposedto electromagnetic radiation, and from a dark state to a faded statewith application of a voltage.
 3. The optical filter of claim 2 whereinthe voltage applied is from 0.1 V to 2.5 V.
 4. The optical filter ofclaim 1 further comprising an ultraviolet (UV) blocking layer thatcomprises part of the stack, wherein the UV blocking layer has a cutoffwavelength of between 370 nm and 435 nm.
 5. The optical filter of claim4 wherein the UV blocking layer blocks about 50% of incident UV light atthe cutoff wavelength.
 6. The optical filter of claim 1 comprising: anLTA in a dark state of less than about 15%; an LTA in a faded state ofgreater than about 5%; and a contrast ratio of at least
 5. 7. Theoptical filter of claim 1 comprising a light transmission value of 1% orless in the dark state and 6% or higher in the faded state.
 8. Theoptical filter of claim 1 comprising a light transmission value of 5% orless in the dark state and 15% or higher in the faded state.
 9. A devicecomprising the optical filter of claim 1, wherein device comprises alaminated glass, an ophthalmic device, an automotive glazing product, oran architectural glazing product.